No. 13 August 2, 2007 · 2007. 8. 2. · SOYBEAN APHID UPDATE There have been many recent inquiries...

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No. 13 August 2, 2007

Inside this Issue...Sunflower Moth Blows into North Dakota . . . . . . . . . . . 1Soybean Aphid Update . . . . . . . . . . . . . . . . . . . . . . . . . . 2Sunflower Maggot Causing Injury in Developing

Sunflower Heads . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Swathing Canola . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Tips for Planting Winter Wheat on Prevented

Plant Acres . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Small Grain Survey Results - July 23-27 . . . . . . . . . . . . 4Updates from USDA Cereal Rust Bulletin,

July 31, 2007 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Soil Sampling after Hail . . . . . . . . . . . . . . . . . . . . . . . . . 5New NC Extension Publications . . . . . . . . . . . . . . . . . . 5Horseweed Seed Facts . . . . . . . . . . . . . . . . . . . . . . . . . . 6Wasp Season and Outdoor Picnics Don’t Mix . . . . . . . . 7Around the State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Weather & Climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Note to Subscribers:There will be no Crop and Pest Report next week,

August 9th. The next scheduled issue of the Crop and PestReport will be August 16, 2007.

SUNFLOWER MOTH BLOWS INTO NORTHDAKOTA

The migratory sunflower moth has been observed inBismarck / Hazelton area in high numbers and in Prosper,Cass County. So, it’s time to get out and scout moresunflowers! The adult is a shiny gray to grayish tan mothabout 0.38 inch long, with a wingspan of about 0.75 inch(see photo). When at rest, the wings are held tightly to thebody, giving the moth a somewhat cigar-shapedappearance. The larva has alternate dark and light-coloredlongitudinal stripes on a light brown body and about 0.75inch long at maturity (see photo).

Life Cycle: The moths are highly attracted tosunflower that is beginning to bloom. Individual femalemoths will deposit up to 30 eggs per day on the surface ofopen sunflower heads. The eggs hatch within 48 to 72hours and the newly emerged larvae feed on pollen andflorets. The larvae begin tunneling into seeds uponreaching the third instar (larval growth stage). Thistunneling continues throughout the remainder of larvaldevelopment. Larval development from hatching to fullmaturity takes about 15 to 19 days.

Damage: The young larvae of the sunflower mothfeed primarily on florets and pollen. Older larvae tunnelthrough immature seeds and other parts of the head. Asingle larva may feed on three to 12 seeds and formstunnels in both the seeds and head tissue. Larvae spinsilken threads, which bind with dying florets and frass togive the head a trashy appearance. Severe larvalinfestations can cause 30 percent to 60 percent loss, and insome cases, the entire head can be destroyed. Sunflowerinfested with sunflower moth has an increased incidenceor risk of Rhizopus head rot.

Adult sunflower moth (photo by L. Charlet)

Sunflower moth larva (photo by L. Charlet)

North Dakota State University CROP & PEST REPORT August 2, 2007

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Scouting Method: Sampling sites should be at least75 to 100 feet (23 to 31 m) from field margins. The Xpattern should be used in monitoring a field, countingmoths on 20 heads per sampling site for a total of 100heads. Scouting is most accurate in the early morning orlate evening, when moths are active.

Economic Threshold: The economic threshold forsunflower moth is one to two adults per five plants at theonset of bloom or within seven days of the adult moth’sfirst appearance.

SOYBEAN APHID UPDATEThere have been many recent inquiries about “What

are we seeing for soybean aphid populations in NorthDakota’s soybeans?” So far, populations of soybeanaphids have been hard to find and definitely below theeconomic threshold (


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SWATHING CANOLAIt is important to swath canola at the right time in

order to reduce green seed and losses from shattering. Thebest time to swath to optimize yield and quality is whenthe moisture in the seed is 30 to 35%. Seeds in the pod arecompletely filled and reach physiological maturity atabout 40% moisture. After reaching this stage the seedloses moisture at a rate of about 1 to 3% per day. Seedcolor will change from green to light yellow and finallybrown. The crop may be at the optimum 35% moisturestage for only a few days when weather conditions aredry. As there is usually variability in the field, like loweror higher spots, the crop may not mature evenly. Althoughone could swath different areas of the crop on differentdays this may be impractical and a decision to swathshould be based on the area with the highest yieldpotential. Swathing should be done when 30 to 40 percentof the seeds on the main stem have turned from green tobrown. Most of the seed that will have changed color willbe on the bottom third of the stem.

Canola is usually ready to be cut and put in the swath20 to 30 days after the end of flowering, which is definedas the time when only 10% of the plants still have someflowers. It is important to make the swathing decisionbased on actual field observations considering ridges, soiltypes, plant density, and other field factors.To determine the right time to swath consider only podson the main stem.

Avoid swathing during hot (>86 degrees F) and dryweather. Swathing during the cooler evening hours, atnight, or early morning will allow the seed to dry down ata slower rate. This may lower the chance of green seed inthe end product. Swathed canola is ready to harvest, undernormal conditions, 5 to 14 days after cutting the crop. Ifthere is still green seed in the pods allow a few extra daysin the swath for more color change. Green seed maychange color in the swath but it does not change much

once the crop is combined and put into storage.For more information about canola harvest see the

extension publication A-1171 at: http://www.ag.ndsu.edu/pubs/plantsci/crops/a1171w.htm

Hans KandelExtension Agronomist

[email protected]

TIPS FOR PLANTING WINTER WHEAT ONPREVENTED PLANT ACRES

For fields not planted this season due to excessiverainfall, planting winter wheat can be a viable option. Thefollowing are suggestions to help improve the likelihoodof a successful winter wheat crop on prevented plantacres.

1. Consider establishing a "residue" crop. Successfulwinter wheat survival is largely dependant on goodsnow cover in the winter. During the past severalyears we have experienced relatively mild wintersand many farmers produced good winter wheat cropson land with little or no residue. Nevertheless,having residue in the field can help catch snow anddramatically reduce the risk of winter kill. Therefore,for fields that had previously been tilled or that havelittle or no stubble, consider establishing a residuecrop. The most effective residue crop is flax plantedin early August. Flax can be established as a lightlyseeded solid stand, in wide rows (i.e. 3-4 feetspacing) or as strips. Strips of flax 3 to 5 feet wideand 15 feet apart have been found to effectively trapsnow while minimally depleting soil moisture. Whenseeding flax in strips or in wide row spacings, thedrill should be set at a high seeding rate (40-60pounds per acre) and drill spouts should be taped shutto obtain the desired spacing. Strips of flax morethan 20 feet apart can be risky as they do not catchsufficient snow in most years. Flax should be seededon or about August 1 and no later than August 15,depending on the region of the state. Establishmentof flax can be difficult if moisture is limited, but inthe regions of the state that have been dealing withexcess moisture this year, that should not be a seriousconcern.

2. Break the Green Bridge - Wheat streak mosaic virus

can be a very serious disease of winter wheat as thereis little or no resistance in currently available winterwheat varieties. The wheat curl mite transmits thisvirus. This mite spreads from volunteer wheat andother grasses that are still green when winter wheat isplanted. To reduce or eliminate the risk of wheatstreak mosaic virus moving on to the establishingwinter wheat this fall, all volunteer wheat and grassyweeds should be destroyed at least two weeks beforewinter wheat planting. When possible do not seed

Optimum moisture stage for swathing canola


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winter wheat closer than 1/8th mile to corn or fieldswith volunteer wheat.

3. Plant at the recommended time - In the northern halfof the state the optimum period for planting winterwheat is September 1 to September 15 and for thesouthern half of the state September 10 to September30. Planting prior to the recommended dateunnecessarily depletes soil moisture reserves,increases risk of disease and may reduce wintersurvival. Later plantings generally do not developwell in the fall and can be more sensitive to winterkill, and potentially be less productive.

4. Use a winter hardy variety. This is especially true ifyou are not planting into residue. The varietiesreleased by NDSU (i.e. Jerry) as well as thosedeveloped in Canada are among the most winterhardy. Data on the winter survival during 2003/2004(the most recent season when we observed largedifferences in varieties to winter survival) of most ofthe currently grown varieties can be found athttp://www.ag.ndsu.nodak.edu/aginfo/smgrains/WWsurvial.htm. Jerry, CDC Buteo and CDC Falcon arevarieties for which seed is readily available in thestate and that consistently have shown good wintersurvival. Though farmers have reported success withvarieties developed for Nebraska (i.e. Wesley,Jagalene and Millennium), there is definitely morerisk of winter kill when they are planted in NorthDakota without residue to help catch snow.

5. Apply phosphorus at or prior to planting. About10-15 lbs of P with the seed can improve winterhardiness. Excessive N prior to winter freeze-up,however, can reduce winter survival.

For the most recent data on winter wheat varietyperformance go to:http://www.ag.ndsu.edu/pubs/plantsci/smgrains/a574.pdf.

Joel RansomNDSU Extension Agronomist - Cereal Crops

[email protected]

SMALL GRAIN SURVEY RESULTS - JULY 23-27 NDSU IPM field scouts are winding down their

survey of small grains, and now will primarily concentrateon late season pests of sunflower, canola and soybean.Only the northern tier of counties generally will havewheat and barley that hasn’t passed soft dough stage. Inthe last full week of July, field scouts surveyed 67 wheatfields and 9 barley fields. For wheat, the average growthstage was very early soft dough, and for barley, theaverage growth stage was soft dough. Wheat:

Wheat leaf rust was reported in 22.4% of surveyedfields, with average leaf rust severity in infected fields at7.4%. As with last week, all areas of the state showedsome wheat leaf rust, except for the far northwestcounties. Tan spot and/or Septoria fungal leaf spotswere observed in almost all fields surveyed. Average leafseverity of tan spot was 10.5% and of Septoria, 9.1%.

Fusarium head blight, or scab, was reported fromthe northeast and east central regions. The average fieldseverity in infected fields was very low, at 0.9%. Loosesmut was observed in 19% of surveyed fields, with anaverage of 4% of the tillers showing symptoms in thosefields. A level of 2% infected seed is generallyconsidered threshold for economic return from seedtreatment.

Barley yellow dwarf observations were made in10.4% of surveyed fields, and bacterial leaf blight in28.4% of surveyed fields, with a wide range of severity insymptomatic fields. Black chaff, the head infection phaseof the bacterium that causes bacterial leaf disease, wasobserved in 19% of surveyed fields. These bacterialinfected wheat fields were primarily in the northeast andeast central regions.

Barley: Of the 9 barley fields surveyed during this last week

of July, most (7) were in the northwest. Very fewdiseases were observed in the northwest, with only onereport of Septoria leaf blotch. In the northeast counties,one field showed leaf rust, one showed spot blotch, andone showed bacterial leaf blight. No other diseases werereported by the IPM scouts in barley this last week.


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UPDATES FROM USDA CEREAL RUST BULLETIN,July 31, 2007

The latest Cereal Rust Bulletin of the USDA CerealDisease Lab in St. Paul, provided an update of theirscientist’s observations on small grain rusts in the upperGreat Plains, during their tour of the region the last fullweek of July. They observed that wheat leaf rust waswidespread and at high severity levels on susceptible andmoderately resistant spring wheat cultivars in researchplots in North Dakota and northwestern MN.

They found a significant increase in leaf rust in wheatcultivars identified to have genes Lr16 and Lr34 for leafrust resistance (such as Knudson and Briggs). They saidthat cultivars postulated to have Lr21 resistance genes arestill highly resistant (cultivars such as RB07, Glenn SteeleND, Faller, and Howard). Observations of leaf rust incultivars previously with very good resistance indicatesthat some shifts in prevalent wheat leaf rust races areoccurring again.

The Cereal Rust Bulletin went on to say that infarmer fields in the area, less severe rust was observedthan in research plots, because of planting of the moreresistant cultivars and the common use of fungicidesprays.

The Cereal Disease Laboratory has identified only asingle common race of wheat stem rust in 2007, fromwheat stem collections made from susceptible “tester”cultivars in the region, and from susceptible winterwheats.

Light infections of barley leaf rust were reported inNorth Dakota, and moderate to severe levels of oat crownrust were observed by the USDA scientists in fields ofoats throughout south central North Dakota.

Marcia McMullenExt. Plant Pathologist

[email protected]

SOIL SAMPLING AFTER HAILHail fell on large areas of eastern ND last week,

totally some fields. Planning for next year is naturally thenext step after dealing with the remaining shreds ofresidue. If the crop was small grain, most of the nitrogen(N) in that crop is in the grain, and mineralization of Nfollowing the hail will be small. Sampling after the middleof August would work out well. There will probably be alot of volunteer grain sprouting and growing from lateAugust through September up until freeze-up. Anyvolunteer grain growth will complicate the residual Nreadings from later soil testing, so earlier testing issuggested. After corn, soybean, dry bean, sunflower andother non-small grain crops, there will be significantbiology taking place in those fields until the soil coolsafter October 1. Waiting until after soil cool-down wouldbe suggested to take into account the N mineralizing inthose fields from now until then. Totaled crop except forsmall grains will act like a green manure, with about 1/3of the N in those crops being made available for the nextcrop. Late fall soil sampling will pick up some of that N.The remainder will act as a small previous crop credit fornext year’s crop.

Dr. Dave FranzenNDSU Extension Soil Specialist

[email protected]

NEW NC EXTENSION PUBLICATIONSExtension Weed Scientists in the North Central

Region have embarked on a plan to develop a series ofextension publications on weed management fromglyphosate. This includes weeds that are or might becomeresistant, troublesome, and tolerant in glyphosate systems.The series will also include glyphosate stewardship /management publications.

The following is a list of publications that are available sofar.• Biology and Management of Horseweed• Biology and Management of Wild Buckwheat• Biology and Management of C. Lambsquarters• Biology and Management of Giant Ragweed• Facts about Glyphosate Resistant Weeds• Understanding Glyphosate to Increase Performance


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These publications are housed at a central web site of: http://www.glyphosateweedscrops.org/

Dr George Kegode, former NDSU Weed Ecologistand I just completed, “Biology and Management ofBiennial Wormwood”. It is not a NC Regional publicationin that it seems to only inflict ND but will be an NDSUExtension publication and will be in the same format asthe other weed publications.

Hardcopies of these publications, including theBiennial Wormwood publication, can be ordered from theNDSU Extension Distribution Center by emailing Ardis [email protected] or calling 701 231-7882.External funding sources paid for the printing but theremight a slight charge for shipping and handling.

HORSEWEED SEED FACTSHorseweed, also known as Marestail, is a common

weed in North Dakota no-till fields. Many know thatbiotypes have become resistant to glyphosate in severalstates in the east and mid-west U.S. A few fact about thebiology may help us.

• Single plants can produce over 200,000 seeds. Verysmall seed (1/16 inch long) with pappus can becarried by wind.

• Seeds are so light that they fall or settle at a rate ofabout 1 foot per second.

• Seeds do not have dormancy and can germinateimmediately after maturity.

• Seeds can germinate under favorable conditions inthe fall, spring or mid-summer.

Previous research had found that horseweed seeds

may travel up to 1500 ft downwind from the motherplants. This distance of travel could easily movehorseweed seed within a field, from a fence line into afield, or from one field in to an adjacent field. However, itwould not account for horseweed seed moving longerdistances to potentially spread glyphosate resistance. Researchers in New York and Delaware wanted todetermine if horseweed seed was capable of moving longdistances in the wind. They described winds in the surfaceboundary layer, which are 2.5 times the height of thecanopy or 15 feet if considering 6 ft tall horseweed.Winds above the surface boundary layer are called theplanetary boundary layer (PBL), which generally havegreater wind speeds. Winds in the PBL would beresponsible for potential long distance seed movement. To sample the PBL, the researchers flew speciallymodified RC planes with samplers downwind from a fieldwith mature horseweed over a 3-day period. The 1730-minute flights were at heights ranging from 128 to 460ft above the ground. Remarkably, horseweed seed wascollected in 13 of the 17 flights regardless of the height ofthe flight.

As a result of collecting horseweed seed at theseheights, the researchers concluded that long distance seedmovement is possible. If seeds were blown into the PBLin early afternoon, an 11 mph wind could move the seed45 to 90 miles. Since winds in the PBL are often greaterand frequently may exceed 40 mph, such wind couldmove horseweed seed over 300 miles. With this longdistance dispersal of seed possible, it is also possible formore rapid or wide-scale introduction glyphosate resistant(GR) horseweed. What might this mean for North Dakota?1. Horseweed is a common winter annual weed in many

no-till fields.2. Horseweed has some natural tolerance to glyphosate.3. Glyphosate-resistant (GR) horseweed is certainly

possible in ND, but GR horseweed has not beenreported to date.

4. Glyphosate-resistant horseweed could develop in afield either from selecting for resistance in that fieldthrough repeated use of glyphosate or it could beintroduced as GR seed.

5. Once GR horseweed is established, the potential formovement beyond the initial infestation is possiblevia wind-borne seed.

6. The best defense against “home-grown” resistance or“wind-blown” resistance is a good offensive plan.Use a tank mix in your burndown herbicide programand treat the horseweed before it exceeds 4 to 6inches in height. It is especially important to controlhorseweed before planting soybeans because in-cropoptions are limited. Effective burndown programsbefore soybeans on seedling or rosette stagehorseweed and other options are described in thepublication, “Biology and Management ofHorseweed”.

Source: Shields, E.J., J.T. Dauer, M.J. VanGessel, and G.Neumann. 2006. Horseweed (Conyza canadensis) seedcollected in the planetary boundary layer. Weed Science54:1063-1067.

Richard ZollingerNDSU Extension Weed Specialist

[email protected]


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WASP SEASON AND OUTDOOR PICNICS DON’TMIX

Wasps like yellowjackets (or hornets - see photo) arebeneficial insects and predators that feed on insectsincluding caterpillars, flies, crickets and other pests. In thelate summer or fall, queens stop laying eggs and their nestdecline. As they start to scavenge for food and drink in thelate summer, their priority changes to sweets and othercarbohydrates. Some wasps become aggressivescavengers around picnics and other outdoors activitieswhere food or drinks are served. Control of scavengingwasps at picnics and other outdoor activities is almostimpossible. No insecticides are available that effectivelyrepel or discourage them. The best strategy is to try andavoid attracting them. For example, waiting to serve foodand drinks until people are ready to eat, and then promptlyputting food away when finished. Dispose of any garbageinto a tight-fitting containers. If wasps are bothering youwhile you eat, do not violently swat at them. This willonly make them more aggressive and maybe sting. Gentlybrush them away or wait for them to fly away. Wasp trapsdo catch large numbers of wasps, but not enough tocontrol or reduce the wasp population in the fall.

Prairie yellowjacket trap(photo by W. Cranshaw, CSU)

Janet KnodelExtension [email protected]

South-Central ND

During the past week (July 24-30), the region receivedrain ranging from 0 inches at Linton to 2.7 inches atMcHenry, based on NDAWN (North Dakota AgriculturalWeather Network). The rainfall in the eastern part of theregion was very timely for row crops. Daily water use bycorn and soybean on July 30 ranged from 0.30 to 0.37inches, based on estimates from NDAWN.

Winter wheat, barley, and field pea harvest should becompleted by August 3. Extension agent reports on winterwheat yields range from 50 to 80 bu/A; barley yields at 35to 90 bu/A, and field pea at 30 to 70 bu/A. Spring wheatharvest also has started. Late-season leaf disease and heatminimally lowered yield and test weight on barley andspring wheat, but scab impact appears minimal. Canolaswathing started the week of July 22. Early-planted cornis silking to blister (R1-2 growth stages). The region’saccumulated corn growing degree days continues to beahead of the long-term average (range of 40 to 240 units),depending on location and planting dates. Soybean are atfull-pod to early-seed development (R4-5 growth stages).Soybean aphid levels generally are low but scoutingshould continue until seed is fully developed in pods (R6).Bean leaf beetles are being observed in Dickey Countysoybean fields. Sunflower are beginning to bloom andfields need to be closely monitored for banded sunflowermoth and seed weevil. A second cutting of alfalfa is inprogress.

Greg EndresArea Extension Specialist/Cropping Systems

NDSU Carrington Research Extension Center [email protected]

Prairie yellowjacket (photo by W. Cranshaw, CSU)


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F. Adnan Akyüz, Ph.D.Assistant Professor of Climatology

North Dakota State Climatologisthttp://www.ndsu.edu/ndsco/

North Dakota State UniversityCROP & PEST REPORTExtension EntomologyHultz Hall 202Fargo, ND 58105-5346

Janet Knodel, Co-EditorEntomology231-7582 phone231-8557 fax

Sam Markell, Co-EditorPlant Pathology231-8866 phone231-7851 fax

Plant Sciences231-7972 phone231-8474 fax

Soils231-8881 phone231-7861 fax

Weeds231-7972 phone231-8474 fax

Ag Engineering231-7261 phone231-1008 fax

Helping You Put Knowledge To WorkThe information given herein is for educational purposes only. References to a commercial product or trade name is made with theunderstanding that no discrimination is intended and no endorsement by the North Dakota Extension Service is implied.

NDSU Extension Service, North Dakota State University of Agriculture and Applied Science, and the U.S. Department of Agriculturecooperating. Duane Hauck, Director, Fargo, North Dakota. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914.We offer our programs and facilities to all persons regardless of race, color, national origin, sex, handicap, age, Vietnam era veteransstatus, or sexual orientation; and are an equal opportunity employer.This publication will be made available in alternative formats for people with disabilities upon request (701) 231-7881.

NDSU Crop and Pest Report http://www.ag.ndsu.nodak.edu/aginfo/entomology/ndsucpr/index.htm

No. 13 August 2, 2007 · 2007. 8. 2. · SOYBEAN APHID UPDATE There have been many recent inquiries...

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Transcript of No. 13 August 2, 2007 · 2007. 8. 2. · SOYBEAN APHID UPDATE There have been many recent inquiries...