Diagnosing Diagnosing Tree Disorders Tree Disorders

in the in the LandscapeLandscape

What is a plant disease?What is a plant disease?

Anything that damages plant healthAnything that damages plant health

Plant pathology deals with infectious Plant pathology deals with infectious organisms that reduce plant health, organisms that reduce plant health, multiply, and spread: biotic diseasesmultiply, and spread: biotic diseases

Plant DiseasesPlant Diseases

Biotic FactorsBiotic Factors– VirusesViruses– Bacteria Bacteria – FungiFungi– NematodesNematodes

Abiotic FactorsAbiotic Factors– Environmental Environmental

ProblemsProblems– HerbicidesHerbicides– Nutritional DeficienciesNutritional Deficiencies– PollutantsPollutants

Damage from herbivoresDamage from herbivores

Animals and RodentsAnimals and Rodents

Insects Insects

MitesMites

NematodesNematodes

Insect Damage IdentificationInsect Damage IdentificationKnow Common Pest Arthropod Groups!Know Common Pest Arthropod Groups!

Numerous lepidopteran caterpillars (ex. Numerous lepidopteran caterpillars (ex. armyworms, armyworms, cutworms)cutworms)Beetles (Order Coleoptera): numerous leaf-Beetles (Order Coleoptera): numerous leaf-feeding and wood-boring pestsfeeding and wood-boring pestsSawflies (Order Hymenoptera)Sawflies (Order Hymenoptera)Various flies (Order Diptera)Various flies (Order Diptera)Various insects with piercing-sucking Various insects with piercing-sucking mouthparts including scales, mealybugs, mouthparts including scales, mealybugs, whiteflies, aphids, psyllids, hoppers, various whiteflies, aphids, psyllids, hoppers, various other members of the Order Hemiptera.other members of the Order Hemiptera.Spider MitesSpider Mites

Symptoms vs. signsSymptoms vs. signs

SymptomsSymptoms are changes in growth or are changes in growth or appearance of a plant in response to a appearance of a plant in response to a damaging factordamaging factor

SignsSigns are evidence of the damaging factor are evidence of the damaging factor

Symptom or sign?Symptom or sign?

DiagnosisDiagnosis

Compare plants with disorder to healthy Compare plants with disorder to healthy plantsplants– Roots, stems, leaves, fruitsRoots, stems, leaves, fruits

Ask questions! Ask questions! – History, conditions, variety, soil, etc.History, conditions, variety, soil, etc.

Hypothesis of causeHypothesis of cause

Diagnosis - ContinuedDiagnosis - Continued

Look for signs of pathogen Look for signs of pathogen – Microscopic examinationMicroscopic examination– Culturing on artificial mediaCulturing on artificial media– Immunological methods (ELISA, etc)Immunological methods (ELISA, etc)– Nucleic acid methods (PCR, etc)Nucleic acid methods (PCR, etc)– Electron microscopeElectron microscope

Look for signs of insect or animalLook for signs of insect or animal– Organism itself, eggsOrganism itself, eggs– FrassFrass– HoneydewHoneydew– WebbingWebbing

What questions do you ask?What questions do you ask?

History: herbicide application, fungicide History: herbicide application, fungicide application, insect activityapplication, insect activity

Pattern: isolated plant, entire field, near Pattern: isolated plant, entire field, near edges, etc? Any spread?edges, etc? Any spread?

Any variety differences?Any variety differences?

Certified planting stock?Certified planting stock?

What are viruses and viroids?What are viruses and viroids?Very small particles of nucleic acid and Very small particles of nucleic acid and protein (viruses) or naked nucleic acid protein (viruses) or naked nucleic acid (viroids)(viroids)

icosahedral rods flexuous rods geminivirus

tospovirus viroid inclusion body

Symptoms of VirusesSymptoms of Viruses

Plum Pox VirusPlum Pox Virus

Bacterial diseasesBacterial diseases

Bacteria are single-celled, prokaryotic Bacteria are single-celled, prokaryotic organism (lack a membrane around the organism (lack a membrane around the nucleus of the cell)nucleus of the cell)Most plant pathogenic bacteria are Most plant pathogenic bacteria are gram negative, which means they do gram negative, which means they do not retain the stain crystal violet when not retain the stain crystal violet when you do a gram stainyou do a gram stain– LPS (lipopolysaccharide) layer around cell LPS (lipopolysaccharide) layer around cell

wall wall

What do bacteria look like?What do bacteria look like?Can’t see with the naked eye unless Can’t see with the naked eye unless there are a LOT of themthere are a LOT of them

Culture on artificial media (some are not Culture on artificial media (some are not culturable on media)culturable on media)

Bacterial disease symptomsBacterial disease symptoms

Fire blightFire blightErwinia amylovoraErwinia amylovora

Apple, pear, mountain Apple, pear, mountain ash, raspberry, ash, raspberry, hawthorne, contoneasterhawthorne, contoneaster

What are fungal diseases?What are fungal diseases?Cause the majority of economically Cause the majority of economically significant plant diseasessignificant plant diseases

Caused by fungi – organisms with Caused by fungi – organisms with threadlike hyphae and reproductive threadlike hyphae and reproductive structures (spores)structures (spores)

Fungal Plant DiseasesFungal Plant Diseases

Root Diseases - Soilborne Root Diseases - Soilborne and Residue borne and Residue borne – CankersCankers– RotsRots– WiltsWilts

Foliar Diseases – Foliar Diseases – Residue borne, wind-Residue borne, wind-blown and rain-splashed blown and rain-splashed sporesspores– Leaf spots and leaf moldsLeaf spots and leaf molds

Fungal symptoms & signsFungal symptoms & signs

Dutch Elm Disease in MontanaDutch Elm Disease in Montana

Beetle Galleries

Lesser European ElmBark Beetle

Staining in twig

Cytospora canker - SpruceCytospora canker - Spruce

Verticillium WiltVerticillium Wilt

Root Rots and DiseasesRoot Rots and Diseases

Wind-thrown Trees

ArmillariaPhytopthora

Sudden Oak Death Sudden Oak Death Phytopthora ramorumPhytopthora ramorum

RhizosphaeraRhizosphaera needle cast needle cast Rhizosphaera kalhkoffiiRhizosphaera kalhkoffii

Rainsplash dispersedRainsplash dispersed

Symptoms:Symptoms:– Reduced needle retentionReduced needle retention– Dead (brown) older needlesDead (brown) older needles– Healthy, new needles do not show signs of Healthy, new needles do not show signs of

infectioninfection

Powdery mildewPowdery mildewObligate Parasite Spores airborne over long distances –

Nematodes: a very small, worm-like Nematodes: a very small, worm-like animalanimal

Pine Wilt NematodePine Wilt Nematode

Piercing Sucking InsectsPiercing Sucking Insects

Insects with Insects with piercing-sucking piercing-sucking mouthparts cause mouthparts cause stippling and/or stippling and/or chlorosis on the host.chlorosis on the host.

Example groups: Example groups: aphids, true aphids, true bugs, bugs, hoppers, scale hoppers, scale

insects, insects, whiteflieswhiteflies

Plant Bugs

Aphids

Sooty MoldSooty Mold

Leaf minersLeaf miners

Insects that produce Insects that produce characteristic characteristic “mines” in leaves by “mines” in leaves by feeding.feeding.

Formed by various Formed by various insects including insects including flies, wasps, moths, flies, wasps, moths, and beetles.and beetles.

birch leafminer

Leaf DefoliatersLeaf Defoliaters

Damage caused to a Damage caused to a plant by insect plant by insect feeding. feeding.

““Skeletonizing” Skeletonizing” results when the results when the veins or the veins or the “skeleton” of the “skeleton” of the leaf is left behind.leaf is left behind.

Grasshoppers

Japanese Beetles

Spider Mite DamageSpider Mite Damage

•• Leaf damage Leaf damage includes flecking, includes flecking, bronzing, bronzing, and/or and/or scorching of scorching of leaves.leaves.

•• Several natural Several natural enemies. Most enemies. Most problematic problematic in heavy in heavy insecticide use insecticide use areas.areas.

twospotted spider mite

Damage by Boring InsectsDamage by Boring InsectsInsects that bore Insects that bore into a stem, or into a stem, or seedheadseedheadDamage often Damage often results in weakening results in weakening or killing the hostor killing the host

Emerald Ash BorerEmerald Ash BorerWhat does the damage look like?What does the damage look like?

1. Canopy starts to thin and water sprouts may start

2. Serpentine feeding just below bark3. Small, D-shaped exit hole4. Woodpecker damage another clue to

infestation

Emerald Ash BorerEmerald Ash BorerWhat does it look like?What does it look like?

1. Adult is metallic green, about ½ inch

2. Larvae are flat bodied, about 1 inch

3. Larvae pupate in the tree and adults emerge from D shaped exit holes

Cottony Ash PsyllidCottony Ash Psyllid

Woodpeckers and SapsuckersWoodpeckers and Sapsuckers

PorcupinesPorcupines

Deer and Elk RubsDeer and Elk Rubs

Drought DamageDrought Damage

Trees will shed leaves Trees will shed leaves and needles to and needles to prevent water lossprevent water loss

Herbicide?Herbicide?

HistoryHistory

Soil analysis or bioassaySoil analysis or bioassay

Tissue analysisTissue analysis

Symptoms of herbicide Symptoms of herbicide injuryinjury

Winter InjuryWinter Injury

Desiccation

Frost Damage

Seasonal Needle CastSeasonal Needle Cast

Planting too deepPlanting too deep

Iron Deficiency - ChlorosisIron Deficiency - ChlorosisCommon in high pH Soils

• Apply sulfur to lower soil pH• Apply chelated iron fertilizer foliar or soil applications

How to be a diagnosticianHow to be a diagnostician

Know the plant involved Know the plant involved – What a healthy plant looks like!What a healthy plant looks like!

Look for symptoms and signsLook for symptoms and signs

Look for patternsLook for patterns

Question the environmentQuestion the environment

Make a diagnosis, and check the facts!Make a diagnosis, and check the facts!

Montana State UniversityMontana State UniversitySchutter Diagnostic LabSchutter Diagnostic Lab

Physical addressPhysical address

121 Plant BioScience Bldg. (PBB)

Mailing AddressMailing Address

119 Plant BioScience Bldg.

P.O. Box 173150

Bozeman, MT 59717-3150

(406) 994-5150

diagnostics@montana.edu

http://diagnostics.montana.edu/