University:
Washington State University
Course:
BIOLOGY 409 | Plant Anatomy
Academic year:

2020
Views:

89

Pages:

62
Author:

slypery5hy

Plant Diseases and Plant Diagnostics Outline • Plant Disease • Plant Pathology Language • Why diagnosing plant problems isn’t easy • Various plant problem symptoms • Diagnosing plant problems – The process and The Questions • Is it a disease? • Plant disease management • How and when to use the diagnostic clinic Plant Disease • Disease = Dis – aise (old Norman/French, 14 C. for lack of ease, lack of comfort, inconvenience) • Pathology = ‘pathos’ (Greek: suffering) study of suffering • Disruption of ‘normal’ • Loss of monetary value • Loss of food value • Loss of aesthetics • Loss of life Plant Disease • For disease to occur three factors must be present and conducive: 1) Susceptible host 2) Virulent pathogen 3) Favorable environment Plant Pathology Language Normal/Healthy = what we expect plant to look like May be a relative term! Chlorotic = yellowing Necrotic = dead tissue (brown, black, grey, tan, white) Wilted = drooping or limp Stunted/Poor Growth = smaller than normal Deformed/Distorted = looks ‘distinctly odd’, no other terms fit the symptom description Plant Pathology Language Abiotic = damage caused by non-living factor referred to as disorder rather than disease Biotic = damage caused by a living organism Pest = insect or arthropod Disease = virus, bacteria, fungi, nematodes, and parasitic plants Disorder = myriad of abiotic issues Sign = physical presence of the (biotic) cause Symptom = the plants response Various Plant Symptoms Bacteria • Tiny • Reproduce rapidly • Infection can be so fast that we have to assume that the infection is far beyond the last symptom • Grow between cells • Infect passively – through natural openings and wounds • Can’t move on their own, often rely on water • Or humans, tools, pests… Bacterial • Ooze • Slime • Smell • Galls/Overgrowth • Wilts • Leaf spots-restricted by leaf veins • Cankers • Rots • Scabs • Blights (darkened/black tissue) Common Bacterial Diseases Leaf spots Rots Fungi ( & Fungi - Like) • #1 cause of plant disease in the world • Largest group of plant pathogens • Mycellium • String/thread like growth • Makes up most of the fungus • Responsible for nutrient uptake, spread of disease, survival • Spores • Often hardened and melanized Bruce Watt, University of Maine, Bugwood.org Florida Division of Plant Industry , Florida Department of Agriculture and Consumer Services, Bugwood.org Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org Fungal ( & Fungal - Like) • Spores • Dry • Cankers • Rots • Leaf spots-often sunken, not restricted • Wilts • Damping off young plants • Scabs • Leaf Curling • Galls Common Fungal Diseases Grey Mold Powdery Mildew Common Fungal Diseases Root Rot Verticillium Wilt Viruses • 2nd biggest problem • Need living tissue • Can’t enter the plant on their own • No plant virucide-aim to control the vectors • Genetic material (RNA/DNA) • Contains a protein coat • Requires a host to replicate • Requires a vector • Can also be spread by pollen, tools, propagation, seeds • Virus testing depends on the vector Viral • Mosaic pattern • Lesions- Chlorotic or Necrotic • Stripes or Streaks • Leaf curling/rolling • Vector • Color change • Deformation/malformation of growth • Vein banding • Wilts • Leaf spots Insects • Bronzed or silver leaves • Bites/Chew marks • Leaf curling/cupping • Frass • Shed Exoskeleton • Eggs • Speckling • Galls • Deformation • Vectors Nematodes • Necrosis • Deformation/abnormal growth • Stunting • Chlorosis • Galls • Wilts (in hot weather) • Short/thick roots • Stem swelling • Water spots on leaves • Vectors Abiotic • Galls/Overgrowth • Wilts • Spots • Cankers • Color change • Abnormal growth • Leaf curling/cupping • Chlorosis • Somewhat uniform Abiotic Causes • Drought • Over-watering • Nutrient imbalance • Soil issues • • • pH Compaction Drainage problems • Herbicide damage • Damage (mechanical, chemical, weather) Herbicide Damage • Galls/Overgrowth • Wilts • Spots • Cankers • Color change • Abnormal growth • Leaf curling/cupping • Chlorosis • Can only be confirmed by laboratory residue testing Abiotic versus Biotic • Abiotic = Non-living • Does not spread to other plants • Same problem can affect other cultivars/species • Does not progress through the plant • Biotic = Living • Spreads to other plants • Problem only affects ‘host’ • Progresses in plant Rapid versus Gradual • Rapid damage usually indicates abiotic • Oopsie with an herbicide • Damage event (lightning strike, cold snap, black thumb, etc.) • Does not progress through the plant • Gradual is more suspect for a disease • Takes time for inoculation, penetration, infection and ultimately impact on plant • Repeated damage can have slow build up • Repeatedly not watering your garden Diagnosing plant problems Why it isn’t easy Poor Growth/Stand • Bacteria • Fungi • Insects/pest (maggots, wireworms, mites, cutworms, ect.) • pH issues • Machinery skips/planting issue • Herbicides • Nematodes Leaf Spots • Fungi • Bacteria • Herbicides • Insects • Viruses • Environment Leaf Curling • Bacteria • Fungi • Viruses • Herbicides • Insects • Heat Yellowing/Chlorosis • Nutrient disorders • Root compaction • pH issues • Bacteria • Fungi • Virus • Insects • Nematodes • Herbicides • Looked at the plant funny Wilting • Nematodes • Bacteria • Fungi • Virus • Root compaction • Herbicides • Nutrient • Weather • Root compaction Diagnosing plant problems The process • Eyes • Microscope • Conversations • Weather patterns • Reading • Historical Knowledge • Host Knowledge • State Knowledge • Culturing Techniques • Molecular Techniques Diagnosing plant problems The Questions • Can you identify the crop/plant species? • What is the growing history? • What was the weather like? • Were any chemicals applied? Rate, etc? • What is the cultivar? • How are the plants grown? • What fertilizer has been applied? Rate? • How many plants affected? • What part of the plant is affected? • When did the symptoms come on? • Soil type? Drainage? • Does this problem seem to be spreading? Diagnosing plant problems The Questions • • What are the symptoms? • Are they unique? • Are they ambiguous? • What often causes these symptoms? • What does your gut tell you? Are there signs? • • • Leaf spots with fruiting bodies (fungal) Oozing (bacterial) See the pest or evidence of its presence (frass, eggs, exoskeleton, etc.) Diagnosing plant problems The Questions • • What is the pattern of the landscape damage? • Large area vs. small area • Same types of plants? What is the pattern of the single damage? • • • Entire plant? Individual branches, sections? Is it getting worse? • • In the same plant Is it spreading to other plants? Diagnosing plant problems The Questions • Widespread = probably a damage event (abiotic) • Random? • Small areas of the same/similar host • • Getting worse • • • Most pathogens have a “diet” HUGE indicator of plant disease Repeated damage occurring • (like not watering…) Southside? • Typically, where more sun exposure • • Bottom of slope? • • Can lead to cold damage in winter and heat/drought stress in summer Water tends to collect in the low spots-often helpful for root rots Exposed area? • Wind wipes away moisture Your Turn… • Imagine you run the clinic and these samples came in: • What steps are you going to take to diagnose the samples? • Is the plant suffering from something biotic, abiotic, bacterial, fungal, viral, nematodes, insects, or none of the above? What’s wrong with the pepper? Broad mite damage Did someone spray the roses? Reaction to powdery mildew Turf problems? Canis lupus famililaris: Dog urine damage Bristlecone pine • Abiotic: Resin drop Madrone • Biotic • Fungal leaf spot • Fungal Canker Kinnickinick (Bearberry) • Biotic • Manzanita Gall Aphid Mahonia • Biotic • Rust • Fungal Leaf Spot Juniper • Possibly Abiotic • Suspected herbicide contact as thistles are dead Kale • Biotic • Chewing invertebrate (possibly slug damage) Osmanthus • Biotic • Variegation: not concerning as is a ‘normal occurrence’ Photinia • Abiotic • Leaf Spot • Biotic • Entomosporium leaf spot (fungal) Spruce • Biotic • Cooley Spruce gall adelgid Insect or Not? • Sapsucker damage Can you tell the difference? • Can you tell the difference between abiotic and biotic problems in plants? Chlorosis (yellowing) Triazine damage Nutrient deficiency Grape fanleaf virus Leaf Curling/Cupping Broad mite damage 2,4-D damage Galls/Overgrowth Ash flower gall mite Imazapyr damage Leaf Spots Ozone/Smoke damage Paraquat damage on corn Bacterial leaf spot Abnormal growth Cracking in tuber due to herbicide Cracking in tuber due to water stress Bronzing Flumiclorac damage *post emergence* Cercospora leaf spot Spider mite damage Canker Pathogen derived canker Herbicide damage canker Browning/Wilting Drought/underwatering Salt damage Herbicide damage Needle cast pathogen Plant Disease Management • Avoidance = plant where pathogen is not present • Exclusion = keep the pathogen out (quarantines/inspections) • Eradication = destroying pathogen Both in a region and on the individual plant • Protection = preventing infection • Genetic Resistance = variety selection • Therapy = reducing disease in a plant that is already infected Plant Disease Management Cultural • Crop rotation • Starve the pathogen • Healthy plants • Planted & harvested correctly • Sanitation • Remove the pathogen • Limit the spread • Cleaning of tools! • Soil spread Plant Disease Management Cultural • Crop Rotation • Need to know your problem • Sanitation • Remove infested material • Disposal of debris • Weeding • Pruning Plant Disease Management Cultural • Barriers (mulch) • Barrier to splashed spores, movement from soil up or stopping movement down to soil • Confuse insects • Plant Nutrition • Healthy plant = better tolerance • More isn’t better Plant Disease Management Cultural • Water Can spread spores AND create helpful pathogen environment • Drought vs. overwater • Reduce humidity Plant spacing, pruning, orientation, shade, ect. • Water appropriately • Pick your battles Mites vs foliar • Timing How to use the diagnostic lab What do we do? • Bacterial • Fungal • Viruses • Nematodes • Insect Identification • Pesticide damage How to use the diagnostic lab What don’t we do? • Pesticide Residue Testing • Soil Health/Nutrient Analysis • Mushroom Identification • Food Safety • Where to find/buy a particular pesticide How to submit a sample • Whole plants whenever possible • Range of symptoms • Healthy plant too • As many photos as needed • Carefully packaged • Kept cool until delivery (to mail or in person) • Delay = decay • Completely fill out submission form WHAT YOU SEE WHAT I SEE

Plant Diseases and Plant Diagnostics

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