Transcript Diagnosing Plant Diseases and Pests

Diagnosing Plant Diseases and
Pests
Sherry Curtis
IPM System
• The best way to control insects and diseases
to prevent them before they get a foot hold in
your garden.
Soil Preparation
• Most important step in your whole gardening
process.
• Soil test
• PH 6.5 ( for most vegetables)
• Maintain adequate fertility
• Till soil in Fall to expose pests
• Keep garden biologically active
– Compost
– Aged animal manure
Plant Selection
• Only plant plants suited to your climate
• Use certified disease free seed
• Select for maximum insect and disease
resistance
• Select sturdy plants with healthy root systems
• Buy plants from reputable growers
• Plant at proper time and temperature
Cultural Practices
• Water in the morning so plants have time to
dry before the evening
• Space plants properly
• Use mulch to reduce soil splash
• Rotate crops yearly
• Stay out of garden when plants are wet
• Remove and dispose of diseased leaves and
plants
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Stake tall plants or put in cages
Time plantings
Inspect plants for insects often
Use approved traps for slugs
Keep down weeds and grass
Biological Controls
• Disease resistance plants
• Biological pesticides
Mechanical Controls
•Plant when soil is workable
•Sanitize stakes, cages, and tools with a light
bleach solution.
•DO NOT use tobacco products ( Mosaic
Virus)
Chemical Controls
• Each pesticide has a different amount of
toxicity.
• Spray on calm days early in the morning.
• Always read pesticide label thoroughly
• Apply at recommended rate
• Use pesticides as a LAST resort.
Diagnosing Plant Problems
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What is the plant?
Have you sprayed the plant with anything?
Define the problem..
Look for patterns.
Examine spread of problem
Determine likely cause
Don’t lock on to your 1st impression
Disease
• Plant+Pathogen+Environment= DISEASE
Fungi
• If caught in phase 1, can be washed off
• If caught in phase 2, it has taken control of
tissue
• If caught in phase 3, take serious control
Powdery Mildew
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Most successful and most common
Doesn’t kill plant
Compromises photosynthesis
Stored in roots
Starts in cool wet weather
Shows up in hot weather
Spores can travel 3,000 miles
Signs of problems
• Fungi-3 dimensional, produces structures,
reproduces on outside of plants, and
responsible for 85% of plant diseases
• Bacteria-dissolves plant cells, leaves look
collapsed ( tomato bacteria can live up to 8
years in soil)
• Virus- Cause slow plant growth, flower drop,
spread by bugs, no known cure, systemic
implant.
Plant Diseases
• Fungal pathogens
– Over 80,000 known
– Cause circular leaf spots
– Stem rot
– Concentric rings
– Wilt
– Dis-colorization
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• Bacterial Pathogens
– Form galls
– Irregularly shaped leaf spots
– Wet rots
– Wilting
– Yellowing and drying
– Over 8,000 in US
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• Viral Pathogens
– Inhibit chlorophyll formation
– Causes mottling
– Stunted growth
– Distorted growth
– Tip die back
– Are parasitic
– Usually debilitate not kill
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• Nematodes
– Microscopic round worms
– Cause disease like symptoms
– Moisture loss
– Wilting
– Stunting
– Foliar nematodes cause angular leaf spots
– Return on 12 year cycle
Beneficial Insects
• Everyone recognizes the familiar Ladybug, or
ladybird beetle. Many species have an enormous
appetite for aphids--one of our most common
plant pests. Others prefer scale insects and mites
and are very effective in reducing infestations.
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• Ladybug larvae are equally relentless predators. Their
colorful, but ferocious appearance often causes
unknowing gardeners to assume that they must be
harmful. Nothing could be further from the truth.
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• The Praying Mantis is another widely-recognized
insect predator. Nymphs and adults alike lie in
wait for an unlucky insect which strays too close,
then strike out to grab it with their modified front
legs.
• Ambush bugs use the same lie-in-wait tactic.
Notice that their front legs are also enlarged
and modified. The bright yellow colors of this
species camouflage them in their favorite
hideout--goldenrod flower.
• The Lacewing Larvae are miniature monsters
when viewed at close range. They are deadly
enemies of small caterpillars, aphids, and
other soft-bodied insects.
• In addition to these flies, many Small Wasps are important
parasites of other insects. Adult parasites range in size from
very small. Most range in size from 2 to 15 mm. Larvae of
most parasites develop inside the bodies of their prey, but
some feed externally or pupate outside the host's body.
These parasites are important in suppressing populations of
many insects. They are important for control of loopers,
cutworms, and aphids.
Plants that Attract Lacewings
Achillea filipendulina - Fernleaf yarrow
Anethum graveolens - Dill
Angelica gigas - Angelica
Anthemis tinctoria - Golden
marguerite
Atriplex canescens - Fourwing saltbush
Callirhoe involucrata - Purple
poppy mallow
Carum Carvi - Caraway
Coriandrum sativum - Coriander
Cosmos bipinnatus - Cosmos
white sensation
Daucus Carota - Queen Anne's
lace
Foeniculum vulgare - Fennel
Helianthus maximilianii - Prairie
sunflower
Tanacetum vulgare - Tansy
Taraxacum officinale - Dandelion
Plants that attract Ladybugs
Achillea filipendulina - Fern-leaf yarrow
Achillea millefolium- Common yarrow
Ajuga reptans - Carpet bugleweed
Alyssum saxatilis - Basket of Gold
Anethum graveolens - Dill
Anthemis tinctoria - Golden marguerite
Asclepias tuberosa - Butterfly weed
Atriplex canescens - Four-wing saltbush
Coriandrum sativum - Coriander
Daucus Carota - Queen Anne's lace
Fagopyrum esculentum - Buckwheat
Foeniculum vulgare - Fennel
Helianthus maximilianii - Prairie
sunflower
Penstemon strictus - Rocky Mt.
penstemon
Potentilla recta 'warrenii’ - Sulfur
cinquefoil
Potentilla villosa - Alpine cinquefoil
Tagetes tenuifolia Marigold - lemon
gem
Tanacetum vulgare - Tansy
Taraxacum officinale - Dandelion
Veronica spicata - Spike speedwell
Vicia villosa - Hairy vetch
Pesticides
• Is damage caused by a pest or could it be a
cultural practice?
• What kind of pest is it?
• Are there non chemical ways to control it?
• Is damage severe enough?
• Is pesticide cost effective?
• Can pest be controlled at this stage of life cycle?
• Do you have the proper equipment and skill?
Which Pesticide will meet your need?
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Chemical VS Biological
Choose product labeled for your plants
Never use on food crop unless directed to
Consider the site
What equipment is necessary
Minimize waste
Choose least toxic product
ALWAYS READ DIRECTIONS
Biological Pesticides
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Some botanicals are broad-spectrum
pesticides.
Botanicals are generally less harmful in the
environment than synthetic pesticides
because they degrade quickly, but they can
be just as deadly to beneficials as synthetic
pesticides.
The manufacture of botanicals generally
results in fewer toxic by-products.
Microbial Pesticides
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Insecticidal Soaps
Horticultural Oils
Diatomaceous Earth
Bacillus Thuringiensis (Bt)
– toxin produced to kill caterpillars
Common Garden Pests
Spider mites
Aphids
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Mealy bugs
Thrips
Cabbage Looper
Potato Beetle
Tomato Horn Worm
Squash Vine Borer
Japanese Beetle
Slug
Scale
Two Spotted mite
Common Diseases
• Powdery Mildew
• Anthracnose
Septoria
Fusarium
References
• www.idlab.ento.vt.edu
• www.ppws.vt.edu/~clinic/