ORCHARDFRUIT PESTMANAGEMENTPrivate Pesticide Applicator Training Manual

ORCHARD FRUITPESTMANAGEMENT

Edited by Don Barry, University of Maine Cooperative Extension &

Gary Fish, Maine Board of Pesticdes Control

2009

PREFACEThe Orchard Fruit category includes private applica-

tors using pesticides in the production of orchard-grownapples, peaches, plums, and pears.

For private certification in this category, applicatorsare tested on this manual and the Pesticide EducationManual (Core Manual). If you can find the time, pleasefill out the evaluation at the end of this manual and mailit, as well as any questions or comments you have, to thePest Management Office, Attn: PAT, 491 College Ave.,Orono, ME 04473.

ACKNOWLEDGMENTSMuch of this manual is adapted from the 2003-2004

New England Apple Pest Management Guide, William M.Coli, University of Massachusetts, editor.

The white tailed deer section is rewritten fromWildlife Damage Management in Fruit Orchards, CornellCooperative Extension Information Bulletin 236, by P.D.Curtis, M.J. Fargione, and M.E. Richmond.

This manual has also borrowed from the U.S.Environmental Protection Agency’s pesticide pages:www.epa.gov/pesticides/index.htm; Pruning WoodyLandscape Plants by Lois Berg Stack, University ofMaine Cooperative Extension, Bulletin #2169. Factsheets written by Dawna L. Cyr and Steven B.Johnson, University of Maine Cooperative Exten-sion, as a part of the University of Maine Coopera-tive Extension Farm Safety Program; as well as TheAgricultural Pocket Pesticide Calibration Guide,edited by Jim Dill and Glen Koehler, UMaineCooperative Extension; and Pest Management Officepest fact sheets by Bruce Watt and Clay Kirby,UMaine Cooperative Extension.

PRECAUTIONSProperly timing treatments and proper sprayer

calibration are as important as the product used. Followdirections on pesticide labels. READ THE LABEL!

Cooperative Extension makes no warranty orguarantee of any kind, expressed or implied, concerningthe use of any of the stated products. Users assume allrisk of application and/or handling, whether he or shefollows recommendations or not. Trade names are usedfor identification only; no product endorsement isimplied, nor is discrimination intended.

A Member of the University of Maine System

Published and distributed in furtherance of Coopera-tive Extension work, Acts of Congress of May 8 andJune 30, 1914, by the University of Maine and the U.S.Department of Agriculture cooperating. CooperativeExtension and other agencies of the USDA provide equalopportunities in programs and employment.

In complying with the letter and spirit of applicablelaws and pursuing its own goals of diversity, theUniversity System shall not discriminate on the groundsof race, color, religion, sex, sexual orientation, includ-ing transgender status or gender expression, nationalorigin, citizenship status, age, disability, or veteran'sstatus in employment, education, and all other areas ofthe University System. The University providesreasonable accommodations to qualified individualswith disabilities upon request.

The University will regard freedom from discrimi-natory harassment as an individual employee andstudent right which will be safeguarded as a matter ofpolicy. Any employee or student will be subject todisciplinary action for violation of this policy. Retalia-tion against anyone who makes a complaint of discrimi-nation or harassment or who is involved in a complaintprocess will not be tolerated.

Questions and complaints about discrimination inany area of the University should be directed to theDirector of Equal Opportunity, The University ofMaine, Room 101, 5754 North Stevens Hall, Orono,ME 04469-5754, telephone (207) 581-1226 (voice andTDD). Inquiries or complaints about discrimination inemployment or education may also be referred to theMaine Human Rights Commission. Inquiries orcomplaints about discrimination in employment may bereferred to the U. S. Equal Employment OpportunityCommission.

First printing 2009, D. Barry & G. Fish, eds.

Orchard Fruit Pest ManagementContents

Chapter 1

INTEGRATED PEST MANAGEMENT(IPM) ............................................. 1

Your IPM plan .............................................. 1

The Maine Apple IPM Program ....................... 2

Chapter 2

PESTICIDES ................................... 3

Chemical pesticides...................................... 3

Biopesticides ............................................... 3

Pesticide toxicity .......................................... 4

Poison Center .............................................. 4

Pesticide selection and timing ........................ 5

Managing pest resistance .............................. 5

label compliance .......................................... 6

Chapter 3

AIR BLAST SPRAYERS .......................... 7

Tree row volume .......................................... 7

Concentrate spraying ................................... 8

Determining pesticide dosage........................ 8

Nozzle setup ............................................... 9

Airblast sprayer calibration ............................ 9

Apple bud stages ....................................... 11

Chapter 4

FUNGAL AND BACTERIAL PESTS .... 12

Apple scab ................................................ 12

Black rot ................................................... 14

Wood rot fungi .......................................... 14

Fire blight ................................................. 15

Flyspeck and sooty blotch ........................... 16

Brown rot ................................................. 16

Black knot ................................................ 17

Chapter 5

INSECT AND MITE PESTS ................. 18

Aphids ...................................................... 18

Apple maggot ............................................ 19

Borers ...................................................... 20

Codling moth ............................................ 21

European apple sawfly ................................ 21

Leafminers ................................................ 22

Plum curculio ............................................ 23

Tarnished plant bug.................................... 24

Mites ........................................................ 25

Chapter 6

VERTEBRATE PESTS ........................... 26

Orchard voles ............................................ 26

White tailed deer ....................................... 29

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Integrated Pest Management (IPM) is a multifac-eted approach to keeping crop damage from pestsbelow economically damaging levels. Instead oftrying to eradicate pests with pesticide sprays, IPMintegrates the best available management options in acomplementary way to create an overall managementplan that is efficient, effective, and sustainable. Thegoal of IPM is not only to save money by organizingyour management approach, but to provide safe,effective, economical, environmentally sound, andsocially sensitive outcomes.

Within IPM, pesticide treatments may still play akey role but cultural practices such as sanitation andhabitat management are the first line of defense inpreventing pest problems. When chemical treatmentsare necessary, selective pesticides are given prefer-ence, and are applied in ways that minimize theirdetrimental effects on nontarget species, especiallythe predators and parasites that attack pests. This iswhy IPM is “integrated”—individual managementdecisions are not isolated but take into account,wherever possible, all aspects of the existing andpotential pest situation in relation to the overallorchard operation to produce economically andenvironmentally optimum results.

INTEGRATED PEST MANAGEMENTThe specific techniques used for integrated pest

management vary with each situation, but there arefundamental activities that define IPM:1. Identify the pests that are the source of the

problem. Correct pest identification is required toidentify optimum solutions.

2. Understand the biology and economics of thepest and the system in which the pest exists.

3. Monitor pests and natural controls. Usestandardized, tested monitoring methods ratherthan basing decisions on haphazard observation.

4. Establish economic injury thresholds. Pestmanagement decisions are based on the potentialdamage from pest infestations, status of naturalenemies, sensitivity of the protected site (such asstage of development of a crop), and the weather.Actions are taken only when the potential damageis sufficient to justify action.

5. Select an appropriate strategy of cultural,mechanical, biological, and/or chemical preven-tion or control techniques.

Cultural practices include habitat modifica-tion and adapting operating procedures so thatpest damage is reduced and natural control isenhanced. Sanitation is the removal or cleaningof sources of pest infestation. Choosing plantvarieties that are resistant to pest injury is acultural control. Other agricultural examplesare adjusting planting time, fertilization,mowing, and harvest operations to have themost beneficial or least detrimental affect onthe pest management situation.

Biological controls are predators, parasites,and diseases that attack pests. Measures can betaken to conserve naturally occurring popula-tions. In some situations where naturallyoccurring biological controls are not effective,they can be introduced from outside sources.

Chemical control involves selecting a pesti-cide with the lowest toxicity to humans andnon-target organisms (including biologicalcontrols), and using it in such a way as toprevent or minimize undesirable environmentaleffects. The lowest effective amount of pesti-cide is applied from carefully calibrated sprayequipment.

6. Evaluate the pest management program andimprove it where possible. This requires keepingmonitoring records, treatment records, anddamage assessment and reviewing them on aregular basis.

YOUR IPM PLANThe most effective use of IPM requires planning

and forethought before problems arise. To get frommerely knowing about IPM to actually doing IPMbegins with formulating an IPM Plan. Plans mayvary according to the unique characteristics of eachfarm but all IPM Plans include:

The method of monitoring pest populations andkeeping recordsThe physical, mechanical, and cultural controlsused to inhibit pests

Chapter One

Integrated Pest Management

2

Action thresholds—pest conditions that demandcontrol actions, including pesticide application.A list of available pesticides to be used when andif other management methods fail.Management restrictions, safety precautions, andother constraints.To begin an IPM Plan, conduct a thoughtful

overview of all likely problems and possible ways tomanage them. Write down your plan to help organizeyour thoughts and preserve your ideas:1. Review damage and spray records, and recollec-

tions of block history, to identify key pests andproblem areas. A map of each block is useful torecord pest hot spots, identify areas that may besources for infestation, identify drift-sensitiveareas, and to plan monitoring and treatmentactions. Review the lessons learned from successand failures of the pest management actions ofprevious years. Set measurable objectives foryour IPM program.

2. Read about the biology of pests and beneficialspecies. For each key pest, consider cultural andsite management tactics that can reduce or replacethe need to use pesticides. Be sure to scheduleenough lead-time to implement the tactics youchoose.

3. Determine what information is needed to makeinformed pest management decisions during thegrowing season. Decide which pests will bemonitored, when, how, and by whom. If monitor-ing requires traps or other supplies, order themearly. Locate key monitoring sites on the blockmaps. Blocks and pests with the most uncertaintyfor treatment decisions should receive highestpriority for scouting.

4. For pests that typically require pesticide applica-tion, review the available options and choosematerials that are most compatible with youroperation and particular objectives. When choos-ing a particular pesticide, be sure to consider itsimpact on the local environment, especially ifenvironmentally sensitive areas are present. Alsoconsider the conservation of beneficial species,resistance management, and how you will complywith worker protection standards. Additionalfactors that can influence pesticide selectioninclude, timing, spray concentration, tank-mixcompatibility, phytotoxicity concerns, alternate orborder row application, etc.

5. Establish an information system to record pesti-cide applications, pest, and weather observations.Organize this information so it complies with allregulations and it will be useful for makingmanagement decisions, clear and understandablefor communicating with employees, and availablefor review in following years.

THE MAINE APPLE IPM PROGRAMThe University of Maine Cooperative Extension

provides IPM support to apple growers by gatheringand disseminating relevant pest observations. Applescab fungus, one of the most serious pests of theNew England apple crop, provides a good example.

An understanding of the apple scab disease cycleindicates that spores are released only during wetconditions. Moreover, new tissue becomes infectedonly if the proper combination of wetness andtemperature are reached and maintained for a giventime. These factors are ignored by historic controlmethods which rely on repeated fungicide applica-tions to provide a continuous protective layer onearly growth even if infectious conditions are absent.

The Apple IPM program collects spore releasedata from field monitoring stations as well as localweather conditions from satellites to accuratelypredict scab infection periods. Growers are alerted toapply protective fungicides only when conditions arefavorable for the spread of primary scab infections.

In addition to efficient pesticide applications,IPM emphasizes other methods of scab control:

Using apple varieties bred for resistance to scab.Removing fallen leaves and fruit to reduce thenumber of over wintering spores.Pruning trees to provide a more open canopy toallow faster drying of wet leaves and improvingspray penetration.

For more information about the University ofMaine Cooperative Extension Apple IPM Program:http://pmo.umext.maine.edu/apple/index.html

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Chapter Two

Pesticides

CHEMICAL PESTICIDESOrganophosphate Pesticides affect the nervous

system by disrupting an enzyme known as cholinest-erase. This enzyme regulates acetylcholine, a neuro-transmitter found in both insects and humans. Mostorganophosphates are insecticides; some are verypoisonous. However, they usually do not persist inthe environment.

Carbamate Pesticides also affect the nervoussystem by disrupting cholinesterase, an enzyme thatregulates the neurotransmitter acetylcholine. Theenzyme effects are usually reversible. There areseveral subgroups within the carbamates.

Organochlorine Insecticides were commonlyused in the past; many have been removed from themarket due to their health and environmental effects,and their persistence (e.g. kelthane).

Pyrethroid Pesticides are synthetic variations ofthe naturally occurring pesticide pyrethrin, which isfound in chrysanthemums. They are chemicallymodified to increase their stability in the environ-ment. Some synthetic pyrethroids are toxic to thenervous system.

BIOPESTICIDESBiopesticides are from certain materials. For

example, canola oil and baking soda can displaypesticidal activity and are considered biopesticides.Biopesticides fall into three major classes:

Microbial pesticides consist of a microorganism(bacterium, fungus, virus or protozoan) as the activeingredient. These pesticides can control manydifferent kinds of pests, although each separateactive ingredient is relatively specific for its targetpest. For example, there are fungi that control certainweeds, and other fungi that kill specific insects.

The most widely used microbial pesticides aresubspecies and strains of Bacillus thuringiensis,better known as Bt. Each strain of this bacteriumproduces a different mix of proteins, and specificallykills one or a few related species of insect larvae.While some strains of Bt control moth caterpillars,other strains are specific for the larvae of flies,mosquitoes or beetles. The affected insect species aredetermined by whether the particular Bt produces aprotein that can bind to a larval gut receptor, whichcauses the larvae to starve.

Pesticide product labels are legal documents thatgovern proper usage. Always read the labelbefore using any pesticide. If you are unsureabout any aspect of proper application, contactthe BPC, the pesticide manufacturer or Universityof Maine Cooperative Extension before use.

YOUR RESPONSIBILITY!READ THE PESTICIDE LABEL FORPRESCRIBED SAFETY EQUIPMENT

AND PRECAUTIONS!Wear the appropriate personal protectiveequipment (PPE) listed on the label. At aminimum you should wear long sleeve shirt,long pants, shoes plus socks, chemicalresistant gloves, and eye protection.Do not allow pesticides to contact your skin.After handling pesticide, wash hands and facebefore eating or smoking.Instruct your family, coworkers and farmlaborers on pesticide safety procedures.Post safety rules and emergency informationwhere workers will see them.Orchardists sometimes need to use pesticidein areas where residences, cropland, pasture,or bodies of water are nearby. Avoid applica-tion when conditions favor drift.

4

PESTICIDE TOXICITYToxicity is a measure of a pesticide’s capacity to

cause injury. This hazard to humans varies by how itenters the body—the route of entry. These routesinclude the respiratory system (inhalation), digestivesystem (swallowing), and the skin (spraying orsplashing on the skin or in the eyes).

The greatest hazard is through the respiratorysystem. The membranes in the lungs are so thin thatabsorption is very rapid (symptoms appear in sec-onds to minutes). Such rapid onset of symptoms isalso expected if pesticides are splashed into the eyes.Oral absorption is the next most hazardous route ofentry; symptoms typically appear within 30–90minutes. Dermal (skin) absorption is less immediatebut it is the most common route of entry; symptomsmay not develop for 18 hours. There is considerablevariation in the rate of penetration through the skinby different materials and formulations. Very highdoses of certain pesticides can produce toxic symp-toms within minutes after dermal exposure.

Acute toxicityAcute toxicity is a measure of the immediate

effects of a pesticide exposure in a short period oftime. This is the basis for pesticide classificationsused on product labels—the toxicity category and thesignal word—that informs applicators of the poten-tial hazards of a particular pesticide.

Chronic toxicityChronic toxicity is the capacity of a pesticide to

cause injury, not immediately, but with repeatedexposures over a period of time. These injuriesinclude birth defects, nervous disorders and benignor malignant (cancerous) tumors. Chronic toxicitywarnings are required for certain pesticides.

Cholinesterase inhibition is a widespread symp-tom of chronic toxicity associated with organophos-phate and carbamate pesticides. Cholinesterase is anenzyme produced by the body to control the trans-mission of certain nerve impulses. Cholinesterase isessential to break down nerve impulses after a signalis transmitted from one nerve to the next. Withoutcholinesterase, these impulses flow continuously andmay overload the entire nervous system. Prolongedexposure to organophosphate and carbamate pesti-cides inhibits cholinesterase activity and may resultin a wide range of symptoms. Tests are available tomeasure the effects of this form of chronic exposureand are recommended for anyone who uses organo-phosphate or carbamate pesticides on a regular basis.

NORTHERN NEW ENGLANDPOISON CENTER

The Northern New England PoisonCenter maintains a telephone hotline torespond to emergency calls from concernedcitizens about poison prevention. Housed inthe Maine Medical Center in Portland, thishotline is open 24 hours a day, 7 days a weekby registered nurses or pharmacists withbackgrounds in critical care. All specialistshave passed a national certification exam intoxicology. The Poison Center staff has accessto a 24-hour interpreter service, with over 140languages available, so callers who do notspeak English are able to receive immediatehelp for emergency calls.

The NNE Poison Center Hotline1-800-222-1222 (emergency only)

http://www.mmc.org/mmc_body.cfm?id=2046202-662-7224 (administration and materials)

email - miller@mmc.org

In case of emergency try to determinewhat the victim was exposed to and what partof the body was affected before you takeaction. Taking the right action is as importantas taking immediate action. If the person isunconscious, having trouble breathing, orhaving convulsions, immediately give first aidand call 911 or your local emergency service.If the person does not have serious symptoms,contact the Northern New England PoisonCenter at 1-800-222-1222. Have the productcontainer with you when you call for assis-tance—remember to act fast!

During an emergency call, tell the physi-cian the chemicals listed on the label, the EPAregistration number, antidotes given on thelabel and other information about the accidentthat could aid in treatment.

Be prepared! Read and post safety rules.On the back of this manual, fill in the phonenumber of your local ambulance service,doctor and hospital. Inform your doctor of anyNotes to Physicians on the pesticide label ofthe pesticides that you plan to use, and get his/her advice about what antidotes should be kepton site.

5

PESTICIDE SELECTION AND TIMINGEach pesticide has a unique set of characteristics

that must be considered before selecting the bestmaterial, including:

applicator and environmental hazardsactivity against the target pesteffects on beneficial insects and mitesrestricted entry and preharvest intervalstank mix compatibilityphytotoxicity riskinteractions with previous pesticide applicationsand likely subsequent applicationsresidual protectionsensitivity to weather during application and totemperature for optimum performanceresistance managementIn addition, there are factors that affect the

timing of every application:growth stage of tree or fruitscouting observationspest lifestageactivity pattern of pest or of honeybees and otherbeneficial speciesthe weather before, during and after applicationBecause of these complex interactions that play

between the target pest, pesticide choice, and appli-cation timing, it is vital to become familiar with thecurrently available pesticide products. The bestresource for Maine fruit growers is the latest NewEngland Tree Fruit Management Guide, whichcovers pesticides used in the production of apples,pears, cherries, peaches, nectarines, apricots, plumsand prunes. For more information, contact theUMaine Cooperative Extension, Pest ManagementOffice. The 2008 edition is available online fromUMass Extension: http://www.umass.edu/fruitadvisor/2008/netfmg/index.html

MANAGING PEST RESISTANCEThe potential for developing a pesticide-resistant

pest population depends on interaction betweenbiological and chemical factors. One consistentlytrue rule is that reducing the number of times apesticide is used decreases the potential for resis-tance to that chemical. Making full use of biological,cultural and other non-pesticidal controls is a keyfactor in preventing resistance because these meth-ods suppress the pest population without the geneticselection pressure that leads to resistance. In addi-tion, natural enemies of pest mites and insects can

actually reduce resistance because the enemies attackboth resistant and susceptible individuals, therebydiluting the breeding advantage of the pesticide-resistant individuals.

Because of the differences among pests andpesticides, a resistance management strategy must betailored for each situation. A strategy that works forone class of pesticides may increase the problem ifused incorrectly for others. For example, combiningtwo types of fungicide has worked to control resis-tant apple scab fungus populations. This is becauseindividual scab spores that are resistant to onefungicide are still killed by the other. But combiningtwo or more insecticides or miticides has been foundto fail because the pest insect or mite population islikely to develop resistance to all of the combinedmaterials creating a multiple-resistant pest. Rotatingamong products with different modes of action sothat any one chemical is used as infrequently aspossible is a better approach for preventing insecti-cide and miticide resistance. Chemical groups withshared mode of action and groups with examples ofcross-resistant pests include:

organophosphate and carbamate insecticidespyrethroid insecticidesorganotin miticidestetrazine miticidesbenzimidazole fungicidessterol inhibitor fungicidesstrobilurin fungicides

For information about the latest version of the NewEngland Tree Fruit Management Guide, contact:

University of Maine Cooperative ExtensionPest Management Office

207-581-3880, or toll-free (Maine only) 1-800-287-0279

6

To manage the development of pesticide resistance:Develop and use an IPM plan that incorporates asmany different control mechanisms as possible.Select early maturing varieties or varieties that areresistant to pests.Avoid broad-spectrum pesticides when a morespecific pesticide will suffice.Maintain beneficial insect populations.Follow label recommendations for rotating ormixing products from different classes based onmodes of action—this is not just different brands.When making multiple applications per season,use alternate products from different mode ofaction classes so that only one generation perseason is exposed to a particular class of pesti-cides. If feasible, rotate products from differentclasses from year to year to reduce selectionpressure when only one application is beingmade.Use insecticides and miticides at labeled rates andspray intervals. Do not reduce or increase ratesfrom manufacturer recommendations; this canhasten resistance development.Sprayer nozzles should be checked for blockageand wear, and be able to handle pressure adequatefor good coverage. Spray equipment should beproperly calibrated and checked on a regularbasis.Time applications against the most susceptible lifestages to gain maximum benefit from the product.At the end of the season remove crop residues, asappropriate, to eliminate food sources and overwintering habitats for pests.

LABEL COMPLIANCE

Federal laws warn that food shipmentsbearing residues of pesticide chemicals inexcess of established tolerances will be contra-band and subject to seizures as “adulterated.”This applies to both raw and processed foods.

The amount of pesticide residue in or on afood material at harvest must fall into estab-lished tolerances, expressed in parts per million(ppm). The actual amount of pesticide chemicalfound in foods at harvest depends, in part, onthe amount applied to the crop and the length oftime since the last application. Therefore,growers are responsible for strictly followinglabel information

Under the current EPA regulations,it is legal to apply pesticides:

at a different rate per 100 gallons dilute thanstated on label as long as the applicationstays within the dose per acre limit;at a lower rate per acre than on label; orless frequently than on label.

It is illegal to:increase amount of pesticide applied peracre (overdosage);use shorter intervals between sprays thanminimum interval stated on label; andshorten intervals to harvest (leaving illegalresidues on crop).

For more information about State andFederal pesticide laws, contact:

The Board of Pesticides Control28 State House Station

Augusta, ME 04333-0028207-287-2731

http://www.thinkfirstspraylast.orgemail - pesticides@maine.gov

QUESTIONS ABOUT PESTICIDES?The National Pesticide Information

Center (NPIC) provides objective, science-based information about a variety of pesticide-related subjects, including pesticide products,recognition and management of pesticidepoisonings, toxicology, and environmentalchemistry. NPIC also lists state pesticideregulatory agencies, and provides links to theirWeb sites.

The National Pesticide Information Centerhttp://npic.orst.edu/

1-800-858-7378email - npic@ace.orst.edu

7

Although there are several application methods,orchard pesticides are most frequently applied usingairblast equipment. These applications are oftenspoken of as either dilute or concentrated. A diluteapplication uses enough water to wet all foliagesurfaces to the point where it just begins to drip fromthe leaves—additional spray would just run off ontothe ground. Dilute applications may require a greatdeal of water and are rarely used in practice.

The more common method of application usesconcentrate sprays. The fine droplets produced byairblast sprayers efficiently cover foliage without thelarge amount of water needed to reach the point ofrunoff. Because the volume of water in the tank mixis lower, the concentration or ratio of pesticideincreases, hence the name concentrate application.Concentrate applications made with airblast sprayerscommonly use 40–80 gallons per acre.

Even though orchardists rarely apply pesticidesas dilute applications, it is necessary to know theamount of water needed for a dilute applicationbecause this is the basis for calculating how muchpesticide to use.

TREE ROW VOLUME AND DILUTEGALLONS PER ACRE

Orchard blocks with different size trees and rowspacings require a different dilute gallonage per acre.By making a few simple measurements and using thetree row volume (TRV) formula, growers canestimate how much water is needed for a dilute sprayto different blocks.

Accurate dosage for pesticides applications orthinning, growth regulator, and calcium sprays is tooimportant (and mistakes are too costly) to leave it toguesswork. Use a folding carpenter’s ruler or tapemeasure, and a pocket calculator, to take relativelyprecise measurements and calculate accurate results.

TRV = (H × W × RLA)TRV = Tree Row Volume H = Average Tree Height W = Average Tree Width (this is twice the distance the

average tree extends from the trunk into the travel row).RLA = Row Length per Acre

= 43,560 sq. ft. ÷ feet between rows (center to center).

Dilute Gallons per Acre (DG/A) = (TRV × 0.7) ÷1,000

The dilute gallons per acre formula uses anaverage value of 0.7 gal. needed to cover each 1,000cu. ft. of tree canopy area. This average value isadequate for practical use. The true value varies fromabout 0.4 gal./1,000 cu.ft. early in the spring to asmuch as 1.0 gal./1,000 cu.ft. on poorly pruned treesin late summer.

Chapter Three

Airblast Sprayer Applications

H

W

Row 1 Row 2

Distancebetween

rows

Tree Row Volume (TRV)= Tree Height x Tree Width x Row length per acre.

DEFINITIONSAll distance measurements are in feet.

Tree Height (H) = Distance from theground to the top of the canopy. Exceptfor trees trained to high clearance.

Tree Width (W) = Looking down a rowfrom one end, the average maximumtree width.

Row Length per Acre (RLA) = 43,560square feet divided by distance betweenrows.

Tree Row Volume (TRV) = Tree Height xTree Width x Row length per acre.

Dilute Gallons per acre (DG/A) = TRV x0.7 gallons divided by 1,000.

Concentrate Gallons per acre (CG/A) =Dilute gallons per acre divided byConcentration (or “X”) factor.

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Example 1: If your trees are 13 feet high, 12 feetwide, and planted with 20 feet between rows, use theTree Row Volume formula to calculate the DiluteGallons per Acre (DG/A)—the amount of water thatmust be applied per acre for a dilute application:

TRV = 13 ft. × 12 ft. × (43,560 sq. ft. ÷ 20 ft.)= 156 sq. ft. × 2,178 ft.= 339,768 cubic feet of tree canopy per acre

DG/A = (339,768 × 0.7) ÷ 1,000= 237,838 ÷ 1,000= 238 gallons per acre

Caution: For very small trees, the TRV dilutegallons per acre can be below 100 gallons. However,these small trees are very inefficient at capturingspray deposit. Therefore, always assume at least 100gallons per acre is needed for a dilute application,even if tree size indicates a lower amount.

CONCENTRATE SPRAYINGA dilute application is also called a 1X spray.

The actual amount of water used to apply pesticide isusually much less than the dilute rate. The actualamount is the Concentrate Gallons per Acre (CG/A).An application that uses 1/3 the dilute amount ofwater is called a “3X” spray. Commonly used sprayconcentrations are 2X, 3X, 4X, 6X, and 8X.

Concentrations above 8X increase the difficultyin getting adequate spray coverage and increase thepotential for phytotoxicity (damage to the trees).

Example 2: For the previous example with 238gallons per acre for a dilute application, what are theConcentrate Gallons per Acre for different com-monly used concentration factors?CG/A = DG/A ÷ Concentration (or “X” factor)

For 2X, CG/A = 238 ÷ 2 = 119 gallons per acreFor 3X, CG/A = 238 ÷ 3 = 79 gallons per acreFor 4X, CG/A = 238 ÷ 4 = 60 gallons per acreFor 6X, CG/A = 238 ÷ 6 = 40 gallons per acreFor 8X, CG/A = 238 ÷ 8 = 30 gallons per acre

The advantages of spray concentrations ofgreater than 3X may be outweighed by a decrease ineffectiveness for some pests (mites, aphids, scale,sporulating scab lesions). Dilute sprays are generallymore effective for applying oil, growth regulatorsand foliar nutrients.

As gallons of water are reduced, errors incalibration or spray pattern become more critical.

Concentrate spraying creates greater sensitivity towind speed (should be no more than 5 mph), dryingconditions, sprayer speed (should be no more than2½–3 mph), and accurate sprayer calibration. Prob-lems with phytotoxicity and incompatibility betweenspray materials also increase with higher concen-trate sprays. The amount of oil used should not bemore than 3 times the recommended rate per 100gallons dilute even if the spray concentration is over3X. The increase in efficiency from using less waterper acre reaches a point of diminishing returns andincreasing problems when spray concentration isincreased beyond 8X.

A 20% reduction from the recommended diluterate pesticide dosage is typically made when thepesticide is applied in a 3X or higher concentratespray. This is based on the idea that, compared to adilute application, less pesticide is needed in aconcentrate spray because less is lost to runoff.Concentrate spray dosage reduction seems to workwell for most pests and pesticides, but it is notappropriate for some growth regulators.

DETERMINING PESTICIDE DOSAGEThe dosage amount listed on labels for pesticides

used on fruit trees is stated in two ways. The firstway is the amount per 100 gallons dilute spray. Todetermine how much pesticide to put in the tankusing pesticide dosage per 100 gallons dilute, usethis formula:

Amount of Pesticide =Amount of Spray Mix × Pesticide per 100 gal. × Concentration Factor “X”

100 gallons

Example 3: If the pesticide label calls for 4 oz. per100 gallons dilute, and you are making 200 gallonsof 3X spray mix, how much pesticide should you putinto the sprayer?Amount of pesticide = (200 gal.× 4 oz.× 3) ÷ 100 gal.

= 2400 oz. ÷ 100= 24 oz. = 1.5 lb.

The second way that application rates are statedis the amount to use per acre of trees. As shownearlier in the TRV formula, trees are a volume targetfor spray. Acreage is a measure of area, not volume.The number of acres does not indicate what the treesize is and the amount of foliage per acre that needsto be covered with spray.

There are conventions used to translate acres intoa volume measure. For example, for apple trees,

9

treating an acre of standard root stock apple trees isassumed to require 400 gallons of solution per acrefor a dilute application. Since very few orchards withtrees this size remain, the “standard” rate must beadjusted to current production practices for dwarfand semi-dwarf rootstocks.

To convert a label amount per acre of “standard”apple trees to the amount needed for your orchard,use the following formula:

Amount of Pesticide per Acre =Amount per acre for “standard” trees × DG/A in your orchard

400 Gallons per Acre

Example 4: If the label calls for 3 lbs. per acre whentreating standard trees, how much pesticide shouldyou use per acre for trees where the dilute gallonsper acre is 180?

Amount of pesticide= (3 lb. × 180) ÷ 400 to use per acre= (540 ÷ 400)= 1.35 pounds per acre

Note: Some pesticide labels recommend a minimumrate per acre regardless of adjustment for TRV.

Always follow the label!

NOZZLE SETUPAirblast nozzles should only be used within their

specified pressure range. Airblast sprayer pressure isusually between 100 and 200 pounds per square inch(psi). Using pressures above 200 psi creates super-fine spray droplets, which significantly increases therisk of spray drift. In addition, hot weather can causesuperfine droplets to evaporate before hitting theirtarget. Using pressures below 100 psi may createdroplet sizes too large to reach their intended targetincreasing the risk of poor coverage. However, thispressure guideline will not apply to your sprayer if itis one of the alternate designs, such as an air shearsprayer that uses low pressure nozzles.

For trees over 10 feet tall, a general guideline isto select nozzles that direct 2/3 of the sprayer outputto the upper half of the tree.

AIRBLAST SPRAYER CALIBRATION1. Mark out a test course of 88 feet.2. Fill the sprayer with clean water only.3. With a moving start, pull the airblast sprayer at the speed you would use to apply pesticide through the length of the test course.4. Record the time it takes to travel the 88 feet.5. Repeat steps 3 & 4 on the return trip.6. Average the two travel times together.7. Calculate Travel Speed (TS):TS = 60 ÷ average time in seconds to travel 88 feet

8. Calculate the Swath Width (SW):For spraying every row,

SW = the distance between rows.For alternate row application,

SW = twice the distance between rows.9. Calculate the desired Gallons Per Minute (GPM) from all the nozzles combined:

GPM = (CG/A) × SW (ft.) × TS (mph)

495

Example 5: For the same orchard as described inExample 5 and a sprayer that takes 20 seconds to travel88 feet, what is the desired gallons per minute for a 3Xapplication applied every row?

Time(sec) to travel 88 feet= 20 sec.Travel Speed (TS) = 60 ÷ 20 = 3 mphSwath Width (SW) = 20 ft. for every-row

applicationCG/A (from Example 1) = 238 ÷ 3 = 79 gal. per acre

Gallons Per Minute = (79 CG/A × 20 ft. × 3 mph)

495= 9.58 GPM

DEFINITIONSAll distance measurements are in feet.

Travel Speed (TS) in miles per hour = 60divided by the number of secondsrequired to travel 88 feet.

Swath (S) for spraying every row = thedistance between rows. For alternaterow spraying, swath would be twice therow spacing if you want the full pesticiderate per acre. It would be only thedistance between rows if you want halfof the full pesticide rate per acre, ap-plied more frequently.

Gallons per minute (GPM) = the gallonsof water pumped out of the sprayer eachminute. This equals the product ofconcentrate gallons per acre x Swath xTravel Speed) all divided by 495.GPM = (CG/A x S x TS) ÷ 495

10

Checking sprayer outputSprayer output can be measured using a nozzle

flow meter or by the sprayer refill method. A com-bined approach using a flow meter to detect worn orplugged nozzles, and the sprayer refill method tomeasure overall sprayer output is recommended.Another method of checking nozzle output is byattaching hoses to the nozzles and collecting theoutput in a bucket or calibration jar. This allows youto determine individual nozzle output and deviation.

Nozzle Flow Meter: Using a flow meter allowsyou to find individual nozzles that deviate more than5% above or below the desired output. (If a nozzledeviates more than 5% below the average, it mayneed cleaning. If it deviates more then 5% above theaverage, it may have a worn orifice and needsreplacement. Recalibrate the sprayer after cleaningor replacing nozzles). Adding together the flowmeter measurements for all of the nozzles on thesprayer gives you the total sprayer output.Sprayer Refill Method:1. Fill the sprayer with water.2. Spray water at normal sprayer pressure for 3

minutes.3. Turn off the sprayer.4. Determine the gallons per minute (GPM) dis-

charged by the sprayer:GPM = gal. needed to refill the sprayer ÷ 3 min.

Making adjustmentsAfter the actual output is calculated, compare it

to the desired gallons per minute output (calculated

in Example 3). Adjust and recalibrate until thevolume is within 5% of the recommended volume.For small adjustments, you can adjust the pressurewithin the recommended range suitable for thenozzles being used. You also can adjust travel speed.If other settings remain the same, increasing travelspeed decreases the amount of spray per acre. Theapplication rate is inversely affected by travel speed.For example, doubling the travel speed will halve theamount of spray mixture applied. However, travelspeed should remain in the range of 1½–3 mph forbest coverage. For large adjustments, you may needto add or subtract nozzles, or change to nozzles witha different output rate.

After adjustments are made, repeat the calibra-tion steps until the desired gallons per minute outputrate is reached. Refer to your operator’s manual formethods of adjustment.

Adjusting for different sized trees in thesame orchard

One way to do this is to use “flip nozzles” thatgive you two nozzle configurations on the samesprayer. More commonly, growers calibrate thesprayer for the largest trees they will spray, and thenshut off nozzles not needed to get good coverage ofsmall trees. This approach may be practical, but itusually results in overspraying smaller trees. A moreexact nozzle configuration for small trees can easilypay for itself in spray material savings, less risk ofdrift, less risk of phytotoxicity, less risk of illegalresidues, and other problems associated with inaccu-rate dosage.

For more information about sprayer calibration, see the latest version of theNew England Tree Fruit Management Guide: UMaine Cooperative Extension,Pest Managment Office, 491 College Ave., Orono, ME 04471-1295.Phone: 207-581-3880, or 1-800-287-0279 (toll-free in Maine only) .

11

PinkIndividual flower buds haveseparated. Pink petals are

visible. Stems fully extended.

BloomA typical leaf whorl has 5–8

blossoms; the king bloom is thefirst to open.

Fruit SetDistinct swelling of set

fruit in each cluster.

Petal FallThe stage during whichflower petals are falling

from the tree.

DormantThis is the overwintering stage.

No swelling visible.

Green TipGreen leaf tissue of the first

leaves (spur leaves) is visiblealong the side of the bud.

Half-inch GreenOne half-inch of green tissue is

visible. Spur leaves beginfolding away from the bud.

Silver TipSwelling noticeable. Bud

scales separate at tip to reveallight-gray leaf tissue.

Tight ClusterSpur leaves have folded back

exposing a tight cluster ofgrowing flower buds.

Many orchard production activities parallel the stages of growth that apple buds pass through as theydevelop into fruit. These named stages are often used as benchmarks for timing pesticide applications.

APPLE BUD STAGES

12

APPLE SCABApple scab is caused by the fungus Venturia

inaequalis. This disease can be devastating to applecrops; severe foliar infection can lead to prematuredefoliation with reductions in fruit quality and yield.Because many commercial cultivars are highlysusceptible to this fungus, and because the Maineclimate provides favorable conditions for infection,apple scab is the most important disease of apples inour area.

The apple scab fungus overwinters on fallenapple leaves that were infected during the growingseason. In autumn, scabby leaves on the orchardfloor grow fungal reproductive structures, known asa pseudothecium or a perithecium, and overwinter inthe leaves. The next spring, usually around green tip,infective fungal spores (ascospores) are producedand discharged into the air when there is sufficientrain (at least 0.01 inch) to wet the leaves. The periodof time that ascospores are released from overwin-tered, infected leaves is referred to as the primary

scab season, and lasts roughly 6–8 weeks dependingon temperatures and frequency of rain.

The first infections of the season, known asprimary infections, can occur on susceptible appletissues (young leaves, petioles, sepals, pedicels andyoung fruit) only if the temperature is favorable andthe tissue remains wet for a certain amount of timeafter the ascospores land; this is known as theincubation period. If an infection occurs, scab lesionsbecome visible in 9–17 days, depending on theaverage temperature during the incubation period.

New scab lesions continue to spread the diseaseby growing and releasing another type of infectivespore known as a conidiaspore. These spores (orconidia) are dispersed by rain or heavy dew, usuallyto other areas of the same tree. If they land onsusceptible tissue, they can cause secondary infec-tions. Each scab lesion can produce conidia for 4–6weeks. After the primary scab season has passed,conidia from new scab lesions are the sole source ofspores for the remainder of the growing season.

Chapter Four

Fungal and Bacterial Pests

Above: Apple leaves infected with apple scab. Darkareas of fungal growth often follow leaf veins. Earlyscabs may have a halo of yellowed tissue, later theyappear velvety as conidia develop. Below: Apple scablesions on fruit. The fungus is edible but not veryappealing.

Fungal colonies with infective spores growas patchy scabs. Conidia spread secondaryinfections to new leaves and fruit

Infected leaf

Scab overwintersin fallen leaves

Ascospores blow onto youngtissue and cause primaryinfections

SUMMER

WINTER

SPRING

Apple Scab Lifecycle

Cross section of an infectedleaf showing a pseudotheciawith overwintering spores

13

Another option is to flail-mow and then applyurea to the “in-row” area that could not be reachedby the flail mower.

Chemical control. Chemical control is essentialin orchards planted with cultivars rated moderatelyor highly susceptible to scab. On these cultivars, thebest strategy is to use fungicides based on leaf-wetness and orchard temperature measurementsduring the primary season. This allows for reductionsin fungicides later in the growing season and lessoverwintering inoculum for the following spring. Formore information, see latest version of the NewEngland Tree Fruit Management Guide.

Managing apple scabScab-resistant cultivars are cultured for disease

resistance and offer the possibility of greatly reduc-ing or eliminating fungicide use. Contact your localUMaine Cooperative Extension Office for moreinformation about scab-resistant cultivars; offices arelisted on the inside of the back cover.

Prune trees to open the tree canopy and promoteair and light penetration. This reduces the amount oftime leaves and fruit surfaces remain wet enough tosupport a potential infection. Opening the canopyalso permits greater penetration of pesticide sprays.

Remove alternate host trees that are untreated,such as flowering crabs and abandoned apple trees,from within 100 yards of an orchard. This reducesthe number of ascospores entering the orchard fromoutside sources to an insignificant level.

Manage fallen leaves. Flail-mowing fallenleaves in autumn or early spring (before bud break),or applying 5% urea to fallen leaves can decrease theamount of spring ascospores by 50–75%. This meansthat for any one infection period, there would beapproximately 50–75% fewer scab lesions comparedto the number of lesions that would develop with nosanitation practice.

If leaf fall is very late, then flail-mowing shouldbe delayed until early spring, but as soon as possibleafter snow cover is gone. If flail-mowing is notpossible, a 5% urea solution (42 lbs. urea/100 gals.water) should be applied to fallen leaves at 100 gals.per acre so that the leaf litter is thoroughly wet.

Black rot infections can occur at three different sites.

Black rot limb cankerLeaf spot from black rotis known as frog-eye Black rot on fruit

Apple scab on young fruit and leaves. Primary infectionsoccur on young leaves, petioles, sepals, pedicels andyoung fruit, but only if the temperature is favorableand the tissue remains wet for a certain amount of time.

14

BLACK ROTBlack rot is caused by the fungus Botryosphaeria

obtusa. Three sites of infection produce three differ-ent symptoms: a limb canker, a leaf spot, and a fruitrot. The name black rot refers to the appearance ofthe fruit rot and limb cankers; the leafspot is knownas frog-eye leaf spot. The fungus can also cause acore rot around the seed cavity in developing fruit.

Frog-eye symptoms on leaves first appear about1–3 weeks after petal fall. Early leaf infections looklike small purple flecks that rapidly enlarge intolesions about 1/8 –1/4 inch in diameter. These spotsresemble “frog eyes” in that they retain a purplemargin and have a light brown-tan center. Fruit(sepal) infections can occur as soon as bud scalesbegin to loosen. These early infections can result inblossom-end rot later in the season.

After petal fall, infections of young fruit begin asreddish flecks that turn into purplish pimples; theseenlarge into dark-brown necrotic areas when the fruitbegins to mature. Later infections of mature fruit arecharacterized by black, irregularly-shaped lesionssurrounded by a red halo. As these lesions expand,they become patterned with alternating brown andblack concentric bands. The flesh of the decayedarea remains firm and leathery.

Infected areas of branches and limbs are reddishbrown and slightly sunken. These cankers can expandto several feet in length. Black rot will rapidlycolonize locations with previous damage, includingold fire-blight cankers and cold-damaged tissue.Fruiting bodies (known as pycnidia) are abundantlyproduced on dead bark, dead twigs, and mummifiedfruit. Throughout the growing season, infectivespores are released when it rains, often infectingnearby tissue. Infected leaves and fruit are regularlyfound below mummies and old fire blight cankers.

The optimal temperature for leaf infection is80°F. The optimal temperature for fruit infectionranges from 68°F–75°F. At these temperatures, aminimum of 4½ hours of leaf wetness and 9 hours offruit wetness must occur for infection.

Managing black rotRemoving cankered wood, mummified fruit, and

chopping or removing pruned wood are importantsteps in the management of this disease. If a blackrot problem persists after implementing these sanita-tion tactics, then multiple applications of fungicidesmay be needed from after petal fall through mid- tolate-August to prevent fruit infections.

WOOD ROT FUNGIOrchard trees are susceptible to many wood-rot

fungi. These fungi are usually opportunistic patho-gens that they invade stressed and/or weakened treesthrough wounds. Infecting the wood within, thesefungi grow up and down the limb or trunk in theoldest wood. Wood rotting fungi will cause a tree toslowly decline for years.

Typical wood-rotting fungi include Chondro-stereum purpureum, Trametes versicolor, Schizo-phyllum commune, and Polyporus hirsutus. Thesefungi can be found on the edge of discolored heart-wood present in most older apple trees. When thefungi move from older wood into younger wood nearthe bark, they can create a canker in the bark.

Managing wood rot fungiThe infective spores that spread wood rot fungi

come from dead or decaying limbs, trees, or stumpson which bract mushrooms have developed. Thisgroup of fungi attacks many species of trees and iscommon in the woods surrounding most orchards.This makes it very difficult to reduce the naturallypresent inoculum. However, practices that promotethe health of trees (i.e., proper nutrition and adequatewater) and that decrease the potential for wounds orbroken limbs (i.e., proper training and pruning) willdecrease the potential for infection and diseasedevelopment by wood rot fungi.

Proper pruningPruning out dead or diseased limbs is an impor-

tant part of disease management but, because infec-tive fungal spores are naturally present, every cut

It may seem quick and easy to remove larger brancheswith a single saw-cut but to avoid damaging the tree,first cut the branch back to a stub.

→Should have cut thebranch here beforemaking a final cut.

15

Bark ridge

Saw blade

Branch collar

The final cut leaves no stub but runs nearly parallelto the trunk, from the the outer edge of the bark ridgein the branch crotch, to just outside of the branchcollar at the base of the branch.

Branch stub

Fire blight takes its name from the crisp, burnedappearance of affected tissue – flowers brown andwilt, and twigs shrivel and blacken.

includes the risk of infection by wood rot fungi.Successful pruning requires that all cuts are made ina way that allows the plant to compartmentalize, orclose off, the wounds and resume healthy growth.Always use the right tool for the job, and make sureit is clean and sharp.

Before removing a branch, look closely at itsstructure. You will recognize the branch collar, aslight swollen area at the base of the lower side ofthe branch, and the bark ridge, a V-shaped region inthe top angle between the branch and the main stemto which it is attached. In order for the plant tocompartmentalize the wound successfully, both thebranch collar and the bark ridge must remain intactafter the branch is removed.

Branches an inch or more in diameter should beremoved with three cuts, because their bark may tearif they are removed in one step, causing irreparabledamage. First cut upward halfway into the branch,one to two feet away from the final cut. Second, cutdownward into the branch one inch out from the firstcut. This will remove most of the branch. Third,make the final cut based on the location of thebranch collar and bark ridge.

A properly pruned branch suffers no splinteredwood or peeled bark, and heals before theheartwood rots.

FIRE BLIGHTFire blight, caused by the bacterium, Erwinia

amylovora, is a sporadic disease in Maine, but it canbe devastating to susceptible cultivars and rootstockswhen it occurs. The bacteria overwinter in barktissues along the edges of cankers that were pro-duced the previous season. Rain or insects candisperse the inoculum from the cankers into theblossoms where the bacteria multiplies profusely,spreading from blossom to blossom by pollinatinginsects. The bacteria penetrate host tissue in thepresence of water, through wounds or natural open-ings. Once inside the host, the pathogen continuesgrowth and kills plant cells.

Flowers, fruit, shoots, branches, roots, and trunkscan become infected. Recently infected tissues lookswater-soaked and may leak a watery, milky to lightorange ooze on humid days. As the tissue dies itturns from dark green to brown and black.

Managing fire blightSuccessful management of fire blight requires an

integrated approach including resistant cultivars androotstocks; removing sources of inoculum; attentionto proper nutrition and irrigation so trees are notoverly vigorous; effective timing of blossom treat-ment, when warranted, to prevent infection; andwhen possible and necessary, rapid response toremove infected tissue before disease progressionand spread.

16

A ifi d h th t i

FLYSPECK AND SOOTY BLOTCHThese diseases are caused by different fungi -

flyspeck is caused by Leptothyrium pomi, sootyblotch by Gloeodes pomigena - but both are normallypresent on the same fruit. They cause only surfaceblemishes but this detracts from fruit appearancewhich lowers fruit quality and market value.

Sooty blotch appears on fruit surfaces as sooty orcloudy blotches with indefinite borders. Blotches areolive green to black and can be removed by rubbingvigorously. Flyspeck looks like true "flyspecks,"characterized by sharply defined, small, black, shinydots in groups of a few to nearly 100 or more.

Both fungi overwinter on the twigs of woodyplants, including apple and pear trees. During spring,spores of the fungi are windblown into and through-out the orchard; fruit infection can occur anytimeafter petal fall, although these diseases usuallyappear on fruit late in the season.

Disease outbreaks are favored by extendedperiods of above-normal summer temperatures,combined with frequent rainfall and high humidity.In drier air they apparently remain inactive. Manyconditions can contribute to maintaining highhumidity in apple tree canopies, and thereforeincrease incidence of sooty blotch and flyspeck.

Managing flyspeck and sooty blotchThese two diseases usually occur at a time when

growers would like to minimize pesticide applica-tions with their restricted entry intervals and days-to-havest limits. Cultural practices can significantlyreduce these disease problems, but fungicides aregenerally required to maintain commercial fruitquality in all except the most northern orchards.

Cultural practices that improve air circulationand drying will reduce the diseases–summer pruning,thinning to break up fruit clusters, mowing, andcutting dense hedgerows or nearby woods.

Using fungicides, sooty blotch is easily con-trolled. In most cases, one or two summer applica-tions provide adequate protection. Flyspeck is moredifficult to control. Timing of fungicide applicationsdepends on rainfall and the fungicides used. Toprevent flyspeck infection, fungicide coverageshould be renewed on or before the depletion date ofthe previous spray.

BROWN ROTBrown rot, caused by the fungus Monilinia

fructicola, is a minor disease of apples and pears butthe most serious disease of stone fruits (cherries,plums, and peaches) in Maine. The disease is highlydestructive and can ruin half or more of all fruitbefore harvest, while the remaining fruit is subject topost-harvest infection.

Brown rot is first seen as brown spots on theblossoms in spring; they are soon entirely blighted.The infection may grow into the woody tissueproducing cankers which can kill the entire twig.Infections of mature fruit first appear as brown spotsthat rapidly consume the entire fruit. Tufts of tanconidia are produced on infected fruit which eventu-ally shrivels and dries into "mummies."

The fungus spends the winter in mummified fruiton the tree, and on the ground in infected twigs. In

Flyspeck and sooty blotch cause only surfaceblemishes but this detracts from fruit appearanceand lowers both fruit quality and market value.

Brown rot overwinters in mummified fruit orinfected twigs. These sites release sporesduring spring to continue the disease cycle.

17

blown by the wind to land on susceptible planttissue. These spores can germinate and infect newtissue during wet periods as short as 6 hours. Infec-tion occurs from April through June especially on thecurrent season's growth.

If the knot has girdled the stem sufficiently tocause its death the infection will stop. Otherwise theknot will continue to expand and produce new sporesin successive years.

Managing black knotBlack knot can be controlled using a combina-

tion of prevention and sanitation.Remove all knots and swellings by pruning 3-4"below the knot during the dormant season; beforeApril 1.Burn, bury, or otherwise remove prunings fromthe area as they may still be an active source ofspores.Severely infected trees should be removed entirely.Cut and remove wild hosts of the disease.Use resistant varieties if disease pressure is high.Preventative sprays may be necessary if nearbydisease sources cannot be eliminated or whenbringing a heavily infected tree back to health.Fungicide treatments should be applied atbudbreak and every week to two weeks, espe-cially before rain, until terminal growth stops.

the spring spores are produced which infect theblossoms and renews the disease cycle.

As with most fungi, the severity of brown rot isdependent on the weather. Summers with highrainfall and humidity lead to the greatest diseaseincidence. The fungus can grow slowly at near-freezing temperatures but it grows best at about 70-75°F. The fungal spores require free water to germi-nate and infect tissues and this water can come fromrainfall or dew. Periods of 30 hours of wetness arerequired to initiate fruit infection and fruit injured byinsects, hail, etc. are more susceptible.

Managing brown rotFruit infections arise from spores which are

produced on recently blighted blossoms and cankers.It is important, therefore, to control the blossomblight phase of the disease.

Remove all fruit from an infected tree, and fromthe ground, and prune out infected twigs afterharvest. Burn, bury, or otherwise remove materialfrom the orchard. This will reduce the number ofspores present in the following season.Destroy wild Prunus spp. in the vicinity of theorchard. These wild hosts may harbor the fungus.Prune the trees to maintain good air circulationwhich will promote rapid drying.Fungicide applications to control the blossomblight phase are important. Fruit should also beprotected during the three week period beforeharvest.

BLACK KNOTBlack Knot, caused by the fungus Apiosporina

morbosa, is one of the most common diseases ofplum and cherry in Maine. It can severely limit theproduction of these fruit trees.

Symptoms first appear during Autumn as aninconspicuous swelling on the current season'sshoots. The fungus over-winters in the stem anderupts during the next spring. As the bark splits,knots emerge, greenish and soft at first but becominghardened and black by the end of the second year.

The fungus produces infective spores duringspring rains which are splashed by the rain and

Black knot appears as obvious hard, black andelongated swellings or knots, 1-6" or more inlength. The knots are scattered throughout thetree, increasing if left untreated.

18

APHIDSThere are five species of aphids commonly

found on apples: apple grain aphid, rosy apple aphid,apple aphid, spirea aphid and the woolly apple aphid.The species can be distinguished by their color, thetime of year when they are present, and by differ-ences in the cornicles, which are small, pairedprojections at the rear of the abdomen. Aphids feedon foliage using needle-like mouthparts to suck outplant juices. When present in high numbers, certainspecies can cause leaves to curl and cup and reducetree growth and vigor. Aphids usually overwinter inthe egg stage on twigs, around buds or in barkcrevices.

Woolly apple aphids, Eriosoma lanigerum,have a complex life cycle that involves either appleor elm trees, or both. On apple trees they can befound at feeding sites above the ground in barkcrevices, pruning cuts, wounds, leaf axils, andoccasionally the stem or calyx of fruit, or they maybe below ground feeding on the roots. Root feedingproduces knotty galls; extensive feeding can stuntroot growth. Larger nymphs are about 1/16 of an inchin length and have a purplish body, concealed bytufts of “wool” which are actually fine wax strands.Wooly apple aphid populations are usually mostnoticeable in late summer but the above-groundwoolly apple aphid population is not a reliableindication of the root-feeding population.

Managing aphidsBiocontrols, especially certain species of tiny

parasitic wasps, play a key role in keeping aphidpopulations below pest status. If an insecticidetreatment is more detrimental to thewasp population than the aphids, aspray may actually increase aphidnumbers. For thresholds, monitor-ing techniques and pesticiderecommendations for the variousaphid species, see the latestversion of the NewEngland TreeFruit Manage-ment Guide.

Chapter Five

Insect and Mite Pests

Woolly apple aphids. Winged females can migrateto different host trees. Wingless forms have apurplish body concealed by tufts of “wool,” whichare actually fine strands of bluish-white wax.

(A) A rosy apple aphid. The arrow points to one ofthe cornicles which secrete defensive fluids torepel parasitic wasps. (B) The defense is notperfect however, and parasitic wasps are importantnatural controls.

Crown and roots of a young apple tree withthe characteristic galls produced by woollyapple aphids.

A B

The bodies of parasitized aphidsbecome enlarged and roundedas the parasite grows within.After the wasp cuts an exit holeand flies away, all that remains isa hollow shell.

19

AC

B

The apple maggot. (A) Adult fly. The wingsof the adult are marked by four dark bandsand there is a distinct white spot at the baseof the thorax. The abdomen of the femalehas four white stripes; the male has three.(B) Puparium. (C) Larva or maggot.

APPLE MAGGOTThe apple maggot, Rhagoletis pomonella, lives

on wild and cultivated apple, crabapple, and haw-thorn trees. The adult fly is a little smaller than thecommon housefly with wings conspicuously markedby four dusky, wavy bands. The abdomen of thefemale has four narrow, white, cross stripes; the malehas three. There is also a distinct, small white spot atthe base of the thorax. The life span of a femaleapple maggot fly is about 30 days.

Adult emergence begins in June or July, numberspeak in mid-July to early August. Adult flies mateand begin laying eggs beneath apple skin 7–10 daysafter emergence. Eggs hatch in 5–10 days and thelarvae, or maggots, randomly tunnel throughout thefruit, usually avoiding the core. The maggots arelegless, creamy white, sometimes yellowish orgreenish, and about 3/8 of an inch long when mature.Signs of infestation on the outside of the fruit includethe tiny, brownish egg punctures—small, distorted,or pitted areas in the skin, sometimes with a bit ofwhite wax covering the puncture. In addition, rapiddecay occurs along the interior feeding trails whichmay be visible through the skin. After tunneling for2–4 weeks, the maggots bore out of the fruit anddrop to the ground where they burrow into the soil,change to the pupal stage, and spend the winter.There is only one generation per year.

Managing apple maggotAdult flies are monitored with sticky traps, either

red spheres or yellow traps. The red spheres mimicripening apples; yellow traps mimic apple leaves.For increased effectiveness, the traps can be baitedwith apple volatile lures. Place traps in early Julyusing three traps per block hung about head high intrees along the edge of the orchard. The traps shouldbe surrounded by fruit and foliage but not touching

anything and not obstructed from view. Inspect trapsweekly until the end of August; count flies andremove them from the trap at each visit.

Because the eggs and larvae are protected withinthe fruit, control measures are aimed at the adultflies. Treatments should be based on trap counts.Apply a control treatment if an average of 5 flies pertrap is caught within a week (using apple volatiles);use an average of 2 flies per trap if apple volatilesare not used. Suspend monitoring for 14 daysfollowing an insecticide treatment, then clean anyflies off the traps and begin counting again from zeroto see if the threshold is reached again, indicating theneed for another treatment.

Important cultural controls include, removingunsprayed apple, crabapple, and hawthorn trees thatare near the orchard to help to reduce the local applemaggot population. Collect dropped fruits 2–3 timesa week for early varieties and at least once a weekfor later varieties.

(A) Apple maggots tunnel throughout the fruit, usually avoiding the core. (B) Rapid decay occursalong the feeding trails of apple maggots and eventually becomes visible through the skin.

A B

20

BA C

A B C

BORERSRound-headed apple tree borers, Saperda

candida, are boldly striped beetles about 5/8 incheslong that emerge in the month after petal fall. Fe-males generally lay their eggs from late June to earlyAugust, usually within a couple hundred yards of thetree from which they emerged. Trees less than 10years old are preferred for egg laying. Larval tunnel-ing occurs on the trunk from about 4 inches belowground to 1–2 feet above the ground. Their presenceis often reveled by reddish-brown sawdust pushedout of small pinholes in the bark, as well as sunkenor darkened areas of bark, sometimes oozing sap,that overlay areas of feeding damage. If not re-moved, or eaten by woodpeckers, larvae continue totunnel through the trunk, slowly growing for 2–3years before emerging as adults. Affected trees havepoor growth or yellow foliage, and may break off atthe soil line.

Flat-headed apple tree borer, Chrysobothrisfemorata, adults are dark brown beetles about 1/2 inchlong with a metallic luster. They are primarily activein June and July, on the sunny sides of trees. Eggsare laid in bark crevices. The sinuous trails in thebark are visible without cutting into the tree. Eventu-ally, the grubs bore into the wood, leaving tunnelsthat are oval in cross-section. The grubs are legless,with a broad, flattened head end, and a cylindricalbody. Weakened, stressed or strongly leaning youngtrees are most frequently attacked.

Dogwood borer, Synanthedon scitula, and applebark borer, Synanthedon pyri, are both small wasp-like moths that lay eggs in bark crevices, especially

in burr knots and callus tissue around graft unions.Burr knots are rough areas on the bark, usually at orbelow the graft union, where new, secondary rootsare trying to develop. The caterpillars are usuallyless than 3/4 inches long, with an orange tinge. Theybore in the bark, not the wood. Reddish frass (excre-ment) on the surface indicates infestation. Adults flyfrom mid-June through late-August, but most activityis usually in July. The life cycle takes one year.

Managing borersRoundheaded apple tree borers. September,

and again in the spring, are the best times to checktrunks above and below the soil line for smallpinholes exuding reddish sawdust or dark, sunkenareas indicating the presence of boring larvae.Shallow larvae may be dug out with a knife. Larvaein deeper tunnels may be killed with a wire or byinjecting a suitable insecticide with a grease gun.

Trees injured beyond recovery should be re-moved and burned, and nearby trees checked forinfestation. If possible, remove alternate hosts (wildand crab apple, choke cherry, hawthorn, mountainash, shadbush) within 100 yards of the orchard.

Insecticide sprays made against plum curculioand apple maggot also help control adult borers asthey feed on apple foliage. July and August applica-tions that reach trunks not shielded by vegetation orguards also help control hatching larvae. Withoutsummer insecticide coverage there is increased riskof attack, especially to trees less than 10 years old.

Brushing diluted white latex paint onto the lowertrunk may deter egg laying. A white coating alsomakes it easier to detect larval tunnels. Another wayto prevent damage is to ring the lower trunk with aloose fitting barrier (for example, hardware cloth).The barrier should be closed at the bottom withmounded soil, and tied with a cord around the top.Remove barriers after harvest.

Round-headed apple tree borer(A) Larva. (B) Pupa. (C) Adult.

Flat-headed apple tree borer(A) Larva. (B) Pupa. (C) Adult.

The adult dogwood borer is a small wasp-like moth.

21

Dogwood borer and apple bark borer. Con-trolling burr knots helps prevent problems with theseborers. Plant trees with the graft union not more than1–2 inches above ground. Be careful not to buryscion wood. If trees are already in the ground, soilmay be mounded around the trunk in a wide mound(not a narrow cone which may increase winterinjury). Avoid shading and increased humidity at thetrunk due to weeds, sucker growth, opaque voleguards, or debris trapped in vole guards. Dilutedlatex paint applied to the lower trunk beforeegglaying may be an effective deterrent.

CODLING MOTHThe codling-moth, Cydia pomonella, is a pest of

apples, pears and occasionally of other fruits. Theadult moth is small, with a wingspread of only about3/4 of an inch. The brown fore-wings are crossed byirregular gray and brown lines. Adult moths areseldom seen; they fly only at night and are notattracted by lights.

Codling moths overwinter as full-grown caterpil-lars in a protected place, usually under the bark ofthe tree where the insect fed. In the spring it pupatesand the adult moth emerges a week or two after petalfall. After mating, female moths lay 50–75 eggs,singly on leaves, sometimes on twigs or small fruit.

The eggs hatch in about a week, and the caterpil-lars eventually crawl to and enter developing fruit.Considerable frass (excrement) is normally associ-ated with entry holes, which are often near the calyxend. Larval “stings” are shallow holes caused by acodling moth larva taking a few bites but not burrow-ing. A “sting” causes a surface blemish but does notresult in interior breakdown of the fruit. Caterpillarsusually tunnel into the core of the fruit and feed for amonth or so until mature. Tunneled fruits usually fallwith the “June drop.” Full-grown caterpillars burrowout of the fruit and pupate under a loose piece of

bark. Some larvae enter hibernation while otherscontinue development and emerge as second genera-tion adults from the latter half of July into Septem-ber. Second generation codling moth larvae causemore damage than first generation. However, somedamage attributed to second generation codling mothmay actually be caused by oriental fruit moth, lesserappleworm, redbanded leafroller or obliquebandedleafroller.

Managing codling mothProblems with codling moths are infrequent in

Maine because the adults and larvae are usuallykilled by insecticide sprays made for other pests.Where specific codling moth treatments are needed,insecticide applied when egg hatch begins is themost effective strategy. Optimum spray timing canbe estimated by setting up pheromone traps duringbloom to detect the beginning of adult emergence.

EUROPEAN APPLE SAWFLYSawflies are a group of thick-bodied wasps that

do not possess defensive stingers like yellowjacketsor bees. The sawfly’s stinger is an ovipositor (astructure for laying eggs) adapted to saw or drill intoplant tissue, so they only “sting” plants, and thenonly to lay eggs.

Codling moth damage, outside and inside.

The adult codling moth.

22

(C) European apple sawfly damage. Young larvae feedalong the surface of the fruit leaving a curved feedingscar; older larvae bore deep inside the fruit.

(A) Sawflies are a group of thick-bodied wasps that donot possess defensive stingers like other wasps orbees. (B) The larvae look much like caterpillars butthere are seven pairs of prolegs on sawfly larvae andonly five pairs on caterpillars.

A

B

The European apple sawfly, Hoplocampatestudinea, overwinters as a larva in the soil; itpupates in the spring, and adults emerge during latepink and bloom. Adult sawflies can be seen flyingaround blossoming apple trees especially on bright,sunlight days. When they land, sawflies moverapidly with quickly vibrating antennae. The averageadult life span is 1–2 weeks.

Eggs are laid during bloom, at the calyx end ofthe fruit. Young larvae feed just below the skin ofthe fruit, following a spiral path usually toward thecalyx. In mature fruit, this injury persists as a visible,curving scar. Older larvae bore deep inside the fruitand may leave conspicuous amounts of wet, reddish-brown frass (excrement) on the infested apple andnearby fruit. When mature, sawfly larvae drop to thesoil and construct cocoons in which they remain aspupae until the following spring.

Managing sawfliesInsecticides applied at pink and/or petal fall

control this pest. White sticky traps placed beforebloom can help determine the need for a treatment atpetal fall. Traps should be placed near blossoms athead height on the south side of at least one tree per3 acres.

LEAFMINERSTwo species of leafminers are commonly found

in New England apple orchards: apple blotchleafminer, Phyllonorycter crataegella, and spottedtentiform leafminer, Phyllonorycter blancardella.

For many years the apple blotch leafminer was thedominant species in commercial orchards. Howeverin the past several years, the spotted tentiformleafminer has shown a tendency toward moreexplosive population growth and has displaced theapple blotch leafminer in many orchards

Leafmining describes the feeding habit of manytypes of insects. Both of the leafminers discussedhere are small moths that lay eggs on apple foliage;the caterpillars are so small that they can feed on thetissue within the thickness of the leaf. From theoutside of the leaf, the damage they leave is a pale,winding trail or a blotch in the normally green colorof the leaf. The biology and management of both thespotted tentiform leafminer and the apple blotchleafminer are similar.

Both species overwinter as pupae within themines in fallen leaves. Adult moths emerge from theleaf litter and move into tree canopies to mate,generally when trees reach half-inch green to pink.Adult flight and mating activity are most evident onwarm, calm evenings when the temperature exceeds48°F; adults are primarily active at night. Eggs aredeposited on the undersides of leaves and hatch 5–16days later.

Both species of leafminers usually complete 3generations per year. Newly hatched larvae cut theirway between leaf layers and feed on foliar fluids,creating sap-feeding mines which appear as smallwhitish patches on the undersides of leaves. Heavyfeeding damage reduces leaf area which can indi-rectly affect fruit quality leading to smaller fruit,premature ripening and fruit drop, and reduced fruit.

C

23

First-generation larvae are active from petal fallthrough June, second-generation larvae from mid-July to mid-August, and third-generation larvae frommid-August through October. Because generationsoften overlap due to extended periods of egg layingand larval development, it is often difficult to distin-guish between broods.

The two species of leafminers respond differ-ently to traps and exhibit slightly different timing ofemergence and adult flight. For more informationconcerning monitoring, see the latest version of theNew England Tree Fruit Management Guide.

Managing leafminersNaturally occurring biological control agents

play a major role in keeping leafminer populationsbelow economic significance. Maintenance of thesebiocontrol agents through insecticide selection andminimization is an important component of leafminermanagement. When biocontrol fails, there arenumerous pesticide options for leafminer control,falling into three basic strategies: prebloom treat-ments, first-generation mine treatments, and second-generation mine treatments.

For maximum effectiveness with any of thesematerials, treatment decisions should be based onmonitoring of mine density and developmental stage.The best timing for control of first or second genera-tion mines is when sap-feeding mines are visible butbefore more than 10% of the mines progress to thetissue-feeding stage (when mines become visible onthe top surface of the leaf).

PLUM CURCULIOPlum curculio, Conotrachelus nenuphar, is a

native pest that attacks apples, pears, peaches andother stone fruit. This insect is a weevil (a type ofbeetle) with a prolonged snout about 3/16 of an inchlong. Adults are dark brown-black with flecks ofgrey on their bumpy backs. The larvae are C-shaped,white and legless. The adults overwinter in leafdebris in woods and hedgerows near the orchard, andin the orchard itself.

Plum curculio emerge and begin migrating toapple trees during bloom but peak migration usuallyoccurs from petal fall to 14 days after petal fall.Female curculios chew a small cavity in young fruitand turns to deposit an egg; she then turns again andcuts a 1/8 inch curved silt beneath the egg to leave itprotected by a flap of apple tissue. This injury appearsas a small crescent-shaped cut on the fruit. Egglaying and feeding damage can occur as soon as thefruits form, and continues until the apples are about11/2 inches in diameter. The crescent-shaped egg-laying slits become D-shaped scars as the applesgrow.

Most infested fruits drop in June. Fully grownlarvae leave fruit and enter soil to a depth of 1 inchand pupate. Adults of the next generation emergeabout 50 days after the eggs were laid in June, andfeed on maturing apples until they seek hibernationsites.

Plum curculio damage to fruit can beginabruptly, and extensive damage can occur in a singlenight. If the temperature exceeds 70oF for 2 daysbefore petal fall, females may be ready to lay eggs atpetal fall. Humid, calm, warm evenings (especially ifthe temperature is above 70oF), pose the greatestrisk. The risk of plum curculio damage increasesafter there have been 3–4 days of average tempera-ture of 55–60oF, or 2 days with maximum tempera-tures above 75oF, after petal fall.

Above: Leafminer moths are only about 1/8 of an inchlong. (A) The apple blotch leafminer. (B) The spottedtentiform leafminer moth. Below: Leafminer damage.

A B

The plum curculio. (A) Pupa. (B) Legless larva.(C) An adult weevil.

A B C

24

AB

C

D E

To monitor egg laying, check fruit on border rowtrees (especially near woods) for fresh damage.Damage appears as small crescent-shaped egg layingcuts and small hollowed-out feeding cavities. Freshscars show no shriveling of the skin edges, nobrowning of the flesh at the cut, and no crustyexudate. Search as high as is practical in the tree.Damage may be heavier in trees pruned in April orMay, compared to trees pruned earlier or not at all.

Adults can be monitored on warm, humidevenings with a beating tray and a rubber mallet tojar the limb. The new adults move down to theorchard floor during the day and during cool, windyweather. Thus, limb tapping that finds no weevilsdoes not guarantee that they are not present.

Managing plum curculioRemoving unsprayed plum, hawthorn, and native

crabapple trees from near the orchard will reduce thethreat of plum curculio damage, especially the threatof egg laying damage 3 weeks or more after petal fall.

Pick up damaged apples as they fall off the treeand destroy them before the adults emerge.

Insecticide applications for apples are typicallyapplied at petal fall, first cover, and (depending onblock history, scouting, and weather) second cover.For peaches and cherries, applications are made atpetal-fall and shuck-split stages. The shuck splitstage is the point where new fruit is just barelyvisible emerging from the drying floral cup.

If populations of other pests at petal fall arebelow threshold, and there is not a history of plumcurculio damage, it may be possible to delay the firstpost-bloom spray. The most conservative approach is2–3 full block applications. An intermediate ap-proach starts with a full block insecticide applicationright at petal fall followed by border row treatmentsas needed to maintain effective residue on trees atrisk of attack.

TARNISHED PLANT BUGThe tarnished plant bug, Lygus lineolaris,

overwinters as an adult under rubbish, weeds, fallenleaves, etc. The bronzish adult is about 1/2 inch longand marked with yellow and black dashes. Theyoung nymphs are often misidentified as aphids but,unlike aphids, they are extremely active. Adultsbecome active as the weather warms in spring andthey feed on a wide range of weeds, crops, andornamental plants, including apple fruit buds or fruitfrom the time of bud swell until about petal fall.Eggs are layed on host plants and hatch in 7–10days. The complete life cycle may be completed in3–4 weeks. Three to four generations may occur inone year.

Both adults and nymphs feed on plant sap withpiercing-sucking mouth parts. As they feed, theyinject poisonous saliva that causes injury to the planttissues. The buds and developing fruit may be eitherkilled (blind buds), dwarfed or deformed. Fruitdimpling and scabbing is caused primarily fromfeeding damage at tight cluster to petal fall; feedingbefore tight cluster causes flower bud abscission.

Tarnished plant bug populations vary consider-ably between blocks. White sticky traps placed atsilver tip can help determine the need for a prebloomtreatment. Traps should be stapled to stakes or hungon low branches, no higher than knee height, andnear the orchard perimeter. Use at least one trap per3 acres, with at least 3 traps per monitored block.Pesticide applications may be more effective whenapplied on a warm, sunny, calm day when TPB aremost active.

(A) Crescent-shaped scars are a sign of egg-laying(oviposition) by female plum curculios. (B) Theseenlarge to D-shaped scars as the fruit grows.

AB

The tarnished plant bug. (A) The youngest nymphs are1/25 inch long, yellowish green, with four round blackdots on the thorax. (B–D) As nymphs mature, theydevelop wing buds, that become fully developed asadults. (D) Adult tarnished plant bugs are 1/2 inch long.

25

Managing tarnished plant bugDestroying broad leaf weed hosts (such as

mullein, pigweed, and golden rod) in and around theorchard in the fall may decrease the overwinteringtarnished plant bug population. To improve control,avoid mowing or using herbicide between pink andpetal fall because disturbance of alternate hosts in thegroundcover may cause tarnished plant bugs to moveup into apple trees. If dandelion removal beforebloom is necessary, applying insecticide applicationat pink immediately before the dandelion removal tocontrol tarnished plant bugs that are flushed up intothe trees.

MITESThere are two significant mite pests in orchards,

the European red mite (Panonychus ulmi) and thetwospotted spider mite (Tetranychus urticae).Mites are arachnids related to ticks but they are tiny;adults are just a quarter to a half of a millimeter inlength. The first immature stage of both mite species(known as a larva) have only 6 legs; all other imma-ture stages (known as nymphs), as well as the adult,are 8–legged. When temperatures are cool, mitesmay require more than a month to complete ageneration but less then two weeks if the weather isunseasonably dry and warm.

European red mites overwinter as red or orangeeggs on rough bark areas of small limbs and fruitspurs. Egg hatch begins at tight cluster, is about halfcomplete by pink, and finishes by petal fall. Thetwospotted spider mites overwinter as maturefemales on the lower portion of the tree trunks or inorchard groundcover. They become active beforebloom but usually stay on weed hosts beneath thetrees into June. They move into apple trees as theirpopulations increase and weeds decline, or whenthey are disrupted by groundcover management.

These mites have piercing mouthparts and feedon plant juices. Because these mites are foliarfeeders and do not directly damage fruit, low popula-tions can be tolerated. However a severe infestationcan cause leaf bronzing, reduced photosynthesis,fruit size reduction, preharvest drop, poor fruitcoloring, and reduced crop potential for the nextyear.

Mite injury is most likely to be significant in theweeks following petal fall. It is critical that mites arenot allowed to build up during May and June, whenthe trees are most sensitive to even relatively lownumbers of mites (2–5 per leaf). From July on, apple

trees can withstand much higher levels of miteactivity. Accumulations of 500–750 mite days (1mite day = 1 mite per leaf for 1 day) have not causedany apparent damage to fruit in field experiments.

Managing mitesThe many predatory insect and mite species that

prey on pest mites offer naturally occurring biologi-cal control. Unsprayed apple trees rarely have miteproblems because this complex of natural predatorskeeps mite populations low. The best long-termsolution to mite management is natural biologicalcontrol by conserving predatory insects and mites.This requires limiting the use of pesticides that areharmful to beneficial predators. Growers who adjustpesticide selection and application method to maxi-mize the potential for mite predator buildup may nolonger need any miticide beyond prebloom oil sprays.

Apply oil as close to dilute as feasible. Useprebloom chemical miticide as needed but restrictpesticide applications to situations where monitor-ing indicates need.Maintain groundcover, tree, and fruit condition toreduce susceptability to the negative effects ofmite feeding on foliage.Monitor accurately and frequently to detectpotential mite problems as they develop.When a pesticide is needed, select materials withlow hazard to beneficial species. It is also impor-tant to pay attention to potential effects on miti-cide performance of other materials in the tank.Use spot or border treatments whenever possible.Use high volume/low concentrate sprays (1X–3Xspray concentration) from accurately calibratedequipment, insure proper dosage, use appropriateadjuvants, apply during good weather, and driveat a tractor speed that favors good coverage.

The two major mite pests of orchard fruits are (A) theEuropean red mite, and (B) the twospotted spider mite.

A B

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ORCHARD VOLESTwo species of voles (sometimes called meadow

or field mice) can cause serious damage to orchardsin Maine. These rodents damage orchard trees bygnawing on trunks and large roots causing loweryields and tree mortality. Symptoms of vole damageinclude poor shoot growth, small leaves, leaves thatturn off-color early in the fall, and small, highlycolored fruit. Commercial apple cultivars androotstocks are very susceptible to vole feeding.Young trees (1–15 years old), and dwarfing root-stock are the most likely to be damaged. Because ofthe numerous risk factors and high cost of establish-ment of high-density apple orchards on dwarfrootstocks, considerable effort should be made toeliminate voles from the orchard. Good ground covermanagement equals effective vole management.

Meadow voles, Microtus pennsylvanicus, arefound throughout the state. They inhabit the orchardfloor by developing a network of surface trailsthrough the groundcover. They burrow in some soils,and can cause damage several inches below theground surface. An individual meadow vole’sactivity is usually restricted to an area of about 2,000square feet. They produce 5–6 litters per year,averaging about 8 young per litter. Because of theirprolific breeding, a few overwintering voles in thespring can lead to a damaging population in the fall.Meadow voles primarily feed on grasses, herbs, andsedges, although they will also eat seeds and occa-sionally tubers and bulbs, they also chew away areasof bark and cambium near the ground line or fromhigher positions on the trunk reachable from the topof snow cover. Tree damage is possible any time ofthe year, but is most common from late fall to earlyspring when other food sources are scarce. Feedingdamage leaves 1 millimeter-wide tooth marks atvarious angles, these are narrower and less variedthan marks left by rabbits.

Pine voles (Microtus pinetorum, also known aswoodland voles) are present in the southern part ofthe state. They travel in burrows within the drip lineat depths up to 3 feet or more, depending on soilconditions. In solid grass sods they may be almosttotally subterranean, but where the groundcovercontains a high percentage of broadleaf herbs, pine

vole surface trails may be numerous. Most of anindividual pine vole’s activity is within a small areaof about 400 square feet. During the cold months,their activity is largely limited to the undergroundburrows. On apple trees, pine voles feed upon barkand cambium primarily below the soil line, and chewoff small roots up to about pencil diameter.

Monitoring and identificationIt is important to determine if pine voles are

present, because some of the management practicesused for meadow vole are not effective against pinevole. Trapping is too time consuming to use as acontrol measure in large plantings, but it is the bestway to identify which species are present.

Traps placed on the surface most likely will notcapture pine voles. Find subsurface burrows byprobing with your fingers 2–3 inches deep at the dripline, deeper near the trunk. Then, carefully excavatean area of sod or soil just large enough to allow astandard wooden mouse trap to sit flush with thebottom of the underground runway. Place the traplengthwise across the trail with the trip pan in thecenter. Use small chunks of apple, rolled oats, peanutbutter, or a combination as bait. Cover each trap sitewith a shingle to prevent other animals from trippingit and to help relocate it 24 hours later. Trap for 3 or4 nights, then repeat a week or two later. Record thenumber of each species caught at each trap.

Tail length is useful for identification. The pinevole tail is very short; about the same length as thehind foot (not leg!), measuring ¾ inch or less. Themeadow vole tail is about twice the length of its hind

Chapter Six

Vertebrate Pests

Voles, sometimes called meadow mice, aresmall, compact rodents with short tails thatburrow underground.

27

foot, reaching 1½–1¾ inches on adults. Pine voleshave chunky bodies, small beady eyes and small earsalmost concealed in smooth brown fur. Meadowvoles have more prominent eyes, larger bodies, andlonger tails than pine voles. Their fur is coarser,more gray than brown.

A long-tailed specimen caught in a trap is likelyto be a white-footed mouse (Peromyscus). The tail ofthis species is well over 2 inches long, and all of itsunder parts are covered with white fur. It has verylarge ears and large eyes. It is reported to eat bark ofyoung trees occasionally, but is generally considereda non-pest in orchards.

Your traps may also catch a shrew, which is abeneficial small mammal; or a mole. Shrews can beidentified by their long pointed snout and needle-sharp front teeth, which are white at the base anddark brown at the tips. (Voles have chisel-shapedfront teeth). Moles can be distinguished from theother groups by their large front feet with outwardfacing palms and prominent digging claws.

Estimating vole activityA general estimate of vole activity is made by

looking for meadow vole surface runways and pinevole tunnels. Pine vole tunneling and feeding may beindicated by spongy soil, burrow entrances with pilesof soil (usually near the base of a tree trunk), andnumerous shoots arising from surface roots. Inaddition, look for injured trees, girdled trunks,chewed prunings, runways in the grass and aroundtrees, or dropped fruit bearing gnaw marks. Note thatvole population density varies even across small areas.

Bait stations are useful to identify areas withvole activity, as well as to assess the overall volethreat in the orchard, and to check 2–3 weeks after a

treatment to see if a follow-up treatment is needed.Bait stations can be made from shingles, split tires,or boards, placed in the grass at the edge of theherbicide strip or drip line. Establish the stations inthe spring or summer to give the rodents time to findand tunnel under the board. Tree flagging helps tofind the stations later. A full block survey requires astation at least every fourth tree in a center row, andalso along a diagonal row across the block.

After harvest, check under each station fortunneling. In each station with a run or tunnel, placea 1-inch thick apple slice in the runway or next to thehole, and then recover it. Check the stations after 24hours. If the percentage of apple slices that havetooth marks (or are entirely missing) exceeds 20%,this indicates potential for serious vole damage. Arecord of repeated assessments over a period ofmonths or years gives a more accurate indication of

To determine the species of voles present in anorchard, monitor using snap traps placed in excavatedburrows. Cover each trap site with a shingle to excludesunlight and prevent other animals from tripping it.

Characteristic Meadow Vole Pine VoleLength (head and body) 3.5–5 inches 2.8–4.2 inches

Tail Length 1.4–2.6 inches 0.6–1.0 inches(at least twice the length (less than or equal to the lengthof the hind foot) of the hind foot)

Adult Fur Coarse, dark brown Soft auburn,mixed with black lacking gaurd hairs

Eye Size Large Small

Nest Placement Usually aboveground, but In burrows, usually lessoccasionally in shallow burrows than 1 foot deep

Food Grasses, sedges, seeds, grain, Bulbs, tubers, seeds, and barkbark, some insects

Damage Usually aboveground, but Girdle crown and rootsoccasionally in shallow burrows

From Tobin and Richmond. 1993. Vole Management in Fruit Orchards. U.S. Department of the Interior, Fish and Wildlife Service.

28

vole activity. These vole monitoring stations can beused later as bait stations for control. The combina-tion of a trail/tunnel survey and apple slice feedingtests gives a better assessment than either methodused alone.

Managing volesA successful vole management program requires

a comprehensive approach that includes individualtree protection and groundcover management. Poisonbaits provide short term population reduction, andare a necessary tool in emergency situations. How-ever, rodenticides are a supplement, not a foundationfor vole management.

Tree guards. Properly installed tree guardsmade of heavy gauge wire or plastic, are veryeffective in preventing most meadow vole damageunless snow depth exceeds guard height. Trunkguards do not prevent underground damage by pinevoles. Embed guards at least 2 inches below thesurface. Avoid close-fitting plastic spiral trunkwraps; they are less effective for voles and providefavorable habitat for trunk-boring insect larvae.

Mowing. Keep orchard floor vegetation below10 inches (below 4 inches is best) with regularmowing. This discourages vole activity aboveground because it leaves them visible to predators.Flail and rotary mowers do a much better job thansickle bar mowers at making orchard ground coverless suitable for voles.

Herbicides. There is little vole activity onground with less than 40% vegetative cover. Whilehay-straw or fabric mulch can exacerbate vole

problems, a NY trial found that wood chip and barkmulch did not. Removing sucker growth, whichattracts voles, also helps suppress meadow voles. Toa lesser degree these practices can reduce pine voleswhich live primarily underground. An effectivemethod for reducing or even eliminating meadowvoles from the orchard is to combine an herbicidestrip that kills vegetation in the tree row, removebrush and weedy areas around the orchard, andpromptly remove or mow dropped apples.

Rodenticides. There are two types of rodenticidebaits for vole control: zinc phosphide and anticoagu-lants. Zinc phosphide baits have been more effectivethan anticoagulant baits against meadow voles. Just 1or 2 fresh grains or pellets of zinc phosphide baitscan quickly kill a vole that eats them, but it may takeseveral days of feeding on anticoagulant baits for thesame effect.

Nontarget hazard. Rodenticide baits may beattractive to domestic pets, birds and other nontargetwildlife. Exposed bait, particularly waxed corn orgrain-based pelletized bait on bare ground, increasesthe chances of nontarget injury. As with all pesti-cides, follow label requirements, use good judgmentand take reasonable precautions to avoid problems.

Rodenticide applicationBroadcast bait application is fast, particularly if

applied with a fertilizer spreader, and can be effec-tive against meadow voles. It is usually not effectiveagainst pine voles. Placing the baits within a weed-free herbicide strip is probably not effective becausevoles avoid open ground. The presence of droppedapples may also make baiting ineffective, as firmapples are a preferred food for voles. Therefore, allsound drops should be removed before broadcastingbait. Wet weather and dark days discourage voleactivity, and wet bait loses potency and palatability.So if the weather is wet and dark during the first fewdays after a broadcast application, the effort iswasted. The best timing for bait application is soonafter a postharvest mowing, and before a 3–dayperiod of sunny, dry weather. Most product labelslimit treatments to the postharvest dormant period.The goal is to reduce the vole population just beforewinter.

Brushy overgrown areas adjacent to a vole-infested orchard are likely to have a population ofthe same species present in the orchard. If theseborder areas are not baited, they will be a source ofreinfestation to the treated orchard.

A T-tube bait station made from 1½ inch PVC pipe.Place traps upright, held by a stake or tied to a treetrunk. A cap or can placed over the vertical feed pipekeeps out sunlight and rain, and allows baiting aftersnow has fallen.

Cap

12–18inches

Cut endsat 45°

Bait

24–36 inches

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WHITE TAILED DEERWhite tailed deer, Odocoileus virginianus, can

cause serious economic losses in orchards. Beyondimmediate yield reduction, deer feeding interfereswith scaffold and leader training, delays growth andyield on young trees, and even kills small trees. Thepotential for damage increases in orchards withsmaller trees where more fruit buds are within reach.

Deer browsing is characterized by ragged brokenends on branches. A systematic survey of 10% of thetrees in an orchard provides a quick, accurate assess-ment of deer damage. If browsing pressure is severe,a long-term plan is needed. The plan should considermethods of exclusion, habitat modifications, andreducing the local deer population. Where there ispotential for significant economic damage, herdreduction alone is probably inadequate. Exclusionand habitat modification require more initial effortand expense, but provide more complete and long-term management.

Managing deerFencing is the most common exclusion tech-

nique. In general, all newly planted orchards shouldbe protected by a deer fence. Deer can be success-fully excluded from large areas with an 8 foot highwoven-wire fence with one or more smooth, high-tensile wires added above to increase fence height to10 feet. This design requires relatively low mainte-nance although the initial cost is high and repairingdamaged sections may be difficult.

Baiting in artificial trails. Although this methodis more expensive than the alternatives, when usedproperly, a tractor-drawn mechanical trail builderallows for more efficient bait application that iseffective against both pine and meadow voles. A trailis made along each side of the tree rows, beyond thewheel tracks, and beneath the drip-line in sod. Aproper depth setting of 2–4 inches, proper timing,and suitable soil conditions are critical for success. Ifthere is vehicle and foot traffic in the orchard afterthe trails are built, or if the soil is too dry, the tunnelswill collapse and bury the poison. If the soil is toowet the poison degrades quickly.

Hand-baiting. Hand-baiting involves theselective placement of baits under established baitstations, or where active trails or burrows are lo-cated. This method makes the most efficient use ofbaits, but requires the greatest time for distribution.When done properly it is likely to be the mosteffective method, particularly for pine voles. Placeteaspoon size, or larger, quantities of bait at eachlocation, at the rate of 2–3 lbs. per acre. Someanticoagulant bait labels specify certain minimumamounts for each placement. To speed bait place-ment, bait stations, such as asphalt roofing shinglesor split tires should be distributed beneath the trees insodded areas well in advance of baiting time. Over aperiod of weeks or months, voles develop trailsunder these bait stations, and trails can be quicklybaited after harvest.

Split tires are available in some areas fromlandfill operators. Split tires have the advantage ofbait placement in shallow cups, and protectedbeneath the tire so that bait does not readily deterio-rate. T-tube bait stations can be made from 1½ inchdiameter PVC pipe. They are placed upright, held bya stake or tied to a tree trunk. A can placed over theupright top keeps out light and rain, and allowsbaiting after snow has fallen. Be sure to check therodenticide label, to be sure this application isallowed; some labels have a very specific definitionof bait stations.

Retreatment with baits. If voles have becomesick yet survived a rodenticide treatment, baitacceptance during a retreatment within a few weekswill be poor. This seems to be a problem more withzinc phosphide baits than with anticoagulants. Tominimize this problem do everything possible tofavor complete control with the first treatment. If asecond treatment is needed, and another type ofrodenticide is legal, use the different type for thesecond application.

The white-tailed deer section is adapted from WildlifeDamage Management in Fruit Orchards. CornellCooperative Extension Information Bulletin 236, 1994.Curtis, Fargione, and Richmond.

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ing pungent chemicals (capsaicin, egg putrescence,predator urine), and bittering agents (denatonium).Odor repellents work better in warm weather; tasterepellents are better during the colder months. Forbest effect, repellants should be applied before deerestablish a feeding pattern. Because repellants do notprovide complete control, some damage must betolerated even if the browsing pressure is low.

Many growers experiment with noncommercialdeer repellents. These materials currently have noEPA registration, and their effectiveness is inconsis-tent. To use small deodorant soap bars, drill a ¼ inchhole through the center of the bar. Leave the wrap-per attached to reduce weathering; with the wrapperin place bars may last several years. Use string orwire to attach the soap to outer branches about 30inches above the ground. There should be no morethan 3 feet between bars within the tree. Caution isadvised as bar soap sometimes increases voledamage when soap residues run down or drip ontothe trunk. Some birds, such as crows, occasionallycause damage to new growth while feeding on soapbars.

Human hair can be applied in mesh bags (1/8 inchmesh or less) hung in mid-fall and early spring in thesame distribution pattern described for soap bars.Additional applications may be necessary in wetseasons. Light cloth bags filled with ½ to 1 cupanimal waste can be used in the same way.

None of the existing repellents provide reliableprotection when deer density is high but they may becost-effective where the expected degree of damageis not far above a tolerable level, or where just asmall acreage is threatened, and if only 2–3 annualapplications are needed for adequate control. In othersituations, exclusion combined with herd reduction isthe most economical long term choice.

A variety electric fence designs are also avail-able. Electric high-tensile fences are usually de-signed as behavioral deterrents. Deer can be ex-cluded with a 5–6 foot electric fence even thoughthey can easily jump over this height. When properlyinstalled, high-tensile electric fences are easilyrepaired, and the initial cost is only half as much asan 8 or 10 foot woven-wire design. However, fencevoltage for electric designs needs frequent monitor-ing, and vegetation control along the fence line isrequired to maintain shocking power. Electric fencingis also susceptible to lightening strikes; adequatelightning protection is an important component.

Guard dogs contained by an “invisible” fence isanother way to exclude deer. This system uses aburied perimeter wire that broadcasts signals tospecialized dog collars. As dogs approach theperimeter, the collars begin to beep, a few more stepsproduces both beeps and mild electric shocks thatform a conditioned response in the dogs to remainbehind the boundary. With the proper facilities andmaintenance, certain breeds of dogs can stay in theorchard year round to repel deer. During periods ofheavy snow it may be necessary to break trails sothat the dogs can get around to patrol the orchard.Invisible fence installation and collars cost consider-ably less than a woven-wire or electric wire fence.However, acquiring suitable dogs and training themis necessary for this approach, and maintenance costs(food, veterinarian bills, etc.) should be considered incomparison with other methods of deer exclusion.

Deer can be repelled from orchards by variousmeans but these methods are usually temporary.Sound generating “scare” devices provide protectionfor only a few days to weeks at best. Several chemi-cal repellents are commercially available. Thesematerials are usually taste or odor repellants, includ-

A slanted 7-wire high-tensile electric deer fence, used where high deer pressures threaten moderate-to-largesized orchards. Deer attempt to go under or through fences that slant toward them but rarely will they jump over.

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