Preventing Insect Problems in
Organic Vegetable Systems
Rick Foster
Department of Entomology
Assumptions
 Small acreages
 High value crops - vegetables
 Diverse production
 Follow organic guidelines
Organic Insect Management
 Principles of management are the same as
conventional IPM (Integrated Pest
Management)
 Only difference is that some options are not
available
 Lack of very effective insecticides requires
greater attention to prevention
Integrated Pest Management
 … a system in which a combination of
methods is used to maintain pest populations
at low levels while allowing for profitable
production with minimal adverse effects on
the environment
(Foster and Flood, 2005)
Integrated Pest Management
 Combination of methods
 Profitable production
 Minimal adverse effects
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Farm workers
Non-target organisms
Consumers
The Life of an Insect
 Goal is to produce viable progeny
 Advantageous to produce lots of young
Challenges for Insects
 Finding a suitable mate
 Finding a suitable food source
 Finding suitable oviposition site (food source
for young)
 Surviving abiotic challenges
 Surviving effects of natural enemies – Rick
Weinzierl will cover
 How can we exploit these challenges to
reduce insect damage?
Finding a Mate
 Most adult insect activity occurs at night
 Many insects communicate with chemicals –
pheromones
Using Pheromones in
Vegetable Pest Management
 Monitoring activity – black cutworms
 Monitoring numbers – corn earworms
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10 moths per trap per night; corn silking
 Mating disruption – diamondback moth and
cabbage looper (larger plantings)
Finding a Suitable Food
or Oviposition Source
 Not all crops are equally attacked
 Not all varieties of a crop are equally attacked
 Timing is important
 Cultural practices are important
Frequency of Insect Damage to Vegetables
Never/Rarely
Sometimes
Usually/Always
Carrot
Green onion
Lettuce
Pea
Radish
Asparagus
Beans
Pepper
Spinach
Tomato
Broccoli
Cabbage
Cantaloupe
Cauliflower
Cucumber
Eggplant
Potato
Squash
Sweet corn
Choice of Varieties
 Most important consideration is what varieties
your customers want to buy
 Not as many examples of resistance to
insects as diseases
 Cabbage – thrips
 Sweet corn – good husk cover: earworms,
tarnished plant bugs, picnic beetles
Timing
 Synchrony between insect’s life cycle and
plant phenology – “window of vulnerability”
 Avoid some problems by planting later – root
and seed maggots
Timing
 Synchrony between insect’s life cycle and plant
phenology – “window of vulnerability”
 Avoid some problems by planting later – root and seed
maggots
 Avoid some problems by planting earlier – corn
earworms
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CEW Moths per Week
Indiana CEW Pheromone Trap Catches
1800
1600
1400
1200
1000
800
600
400
200
0
Lafayette
Vincennes
Date
Cultural Effects
 A healthy, rapidly growing plant can usually
tolerate more damage than one under stress
Cultural Effects
 A healthy, rapid
growing plant can
usually tolerate more
damage than one
under stress
 Too much organic
matter will attract
root and seed
maggots – crucifers,
onions, beans, peas,
corn, cucurbits
Cultural Effects
 A healthy, rapidly growing plant can usually
tolerate more damage than one under stress
 Too much organic matter will attract root and
seed maggots
 Too much nitrogen may attract more aphids
and result in faster reproduction
 Some cultural practices make it harder to find
the plants – reflective mulches, straw mulch
for potato beetle, row covers
Abiotic Effects
 “Winter synchronizes pest populations by
creating a common starting point”
B. R. Flood
Abiotic Effects
 “Winter synchronizes pest populations by
creating a common starting point” – B. Flood
 Insect development is driven by temperatures
– warmer temperatures mean faster
development
 Climatic events such as rainfall or drought
can have a dramatic effect on insect
populations
Abiotic Effects
 Drought (along with hot weather) can result in
outbreaks of mites
 Rainfall can wash insects and mites from
plants
 Frequent rainfall may cause disease
outbreaks in the insect population
Example: Green cloverworm
Additional Information:
www.meisterpro.com
Specific Recommendations
 Not enough time to cover details
 For more specific information, contact :
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Indiana: Rick Foster, rfoster@purdue.edu
Illinois: Rick Weinzierl, weinzier@uiuc.edu
Ohio: Celeste Welty, welty.1@osu.edu
Or your county Extension educator
Plant Early
 Corn earworm or fall armyworm on sweet
corn
 Aphid transmitted viruses on pumpkins
 Imported cabbageworm
 Cabbage looper
Plant Late
 Root and seed maggots
 Seedcorn beetle
 Corn rootworms
 Mexican bean beetles
Host Plant Resistance
 Sweet corn – Stewart’s wilt vectored by flea beetles
Host Plant Resistance
 Sweet corn – Stewart’s wilt vectored by flea beetles
 Sweet corn husk cover: picnic beetles, corn earworm, tarnished
plant bug
Host Plant Resistance
 Sweet corn – Stewart’s wilt vectored by flea beetles
 Sweet corn husk cover: picnic beetles, corn earworm, tarnished
plant bug
 Snap beans: Blue Lake varieties are at higher risk of potato
leafhopper damage than Tendercrop varieties
Host Plant Resistance
 Sweet corn – Stewart’s wilt vectored by flea beetles
 Sweet corn husk cover: picnic beetles, corn earworm, tarnished
plant bug
 Snap beans: Blue Lake varieties are at higher risk of potato
leafhopper damage than Tendercrop varieties
 Potatoes: susceptibility to hopperburn from potato leafhopper is
variable
Susceptibility to Hopperburn
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Delrus – most susceptible
Norland
Monona
Norchip
Atlantic
Superior
Norgold Russet
Kennebec
Red Pontiac
Sebago
Katahdin
Russet Burbank
Russet Norkotah
Ontario
Red La Soda
Nooksack – least susceptible
Host Plant Resistance
 Sweet corn – Stewart’s wilt vectored by flea beetles
 Sweet corn husk cover: picnic beetles, corn earworm, tarnished
plant bug
 Snap beans: Blue Lake varieties are at higher risk of potato
leafhopper damage than Tendercrop varieties
 Potatoes: susceptibility to hopperburn from potato leafhopper is
variable
 Potatoes: variation in susceptibility to potato leafroll virus
vectored by aphids
Host Plant Resistance
 Sweet corn – Stewart’s wilt vectored by flea beetles
 Sweet corn husk cover: picnic beetles, corn earworm, tarnished
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plant bug
Snap beans: Blue Lake varieties are at higher risk of potato
leafhopper damage than Tendercrop varieties
Potatoes: susceptibility to hopperburn from potato leafhopper is
variable
Potatoes: variation in susceptibility to potato leafroll virus
vectored by aphids
Potatoes: Norgold and Norkota (and Norchip) more susceptible
to corn borer injury than Russet Burbank
Host Plant Resistance
 Sweet corn – Stewart’s wilt vectored by flea beetles
 Sweet corn husk cover: picnic beetles, corn earworm, tarnished
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plant bug
Snap beans: Blue Lake varieties are at higher risk of potato
leafhopper damage than Tendercrop varieties
Potatoes: susceptibility to hopperburn from potato leafhopper is
variable
Potatoes: variation in susceptibility to potato leafroll virus
vectored by aphids
Potatoes: Norgold and Norkota (and Norchip) more susceptible
to corn borer injury than Russet Burbank
Glossy or thick (Tropicana) leaves for diamondback moth on
crucifers
Host Plant Resistance
 Sweet corn – Stewart’s wilt vectored by flea beetles
 Sweet corn husk cover: picnic beetles, corn earworm, tarnished
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plant bug
Snap beans: Blue Lake varieties are at higher risk of potato
leafhopper damage than Tendercrop varieties
Potatoes: susceptibility to hopperburn from potato leafhopper is
variable
Potatoes: variation in susceptibility to potato leafroll virus
vectored by aphids
Potatoes: Norgold and Norkota (and Norchip) more susceptible
to corn borer injury than Russet Burbank
Glossy or thick (Tropicana) leaves for diamondback moth on
crucifers
Cabbage – thrips
Host Plant Resistance
 Sweet corn – Stewart’s wilt vectored by flea beetles
 Sweet corn husk cover: picnic beetles, corn earworm, tarnished
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plant bug
Snap beans: Blue Lake varieties are at higher risk of potato
leafhopper damage than Tendercrop varieties
Potatoes: susceptibility to hopperburn from potato leafhopper is
variable
Potatoes: variation in susceptibility to potato leafroll virus
vectored by aphids
Potatoes: Norgold and Norkota (and Norchip) more susceptible
to corn borer injury than Russet Burbank
Glossy or thick (Tropicana) leaves for diamondback moth on
crucifers
Cabbage – thrips
Onions – thrips (antibiosis and tolerance)
Crop Rotation
 Corn rootworms – not western corn rootworm
in some areas
 Corn root aphid
 Wireworms and white grubs
 Colorado potato beetle
 Carrot weevil
 Root and seed maggots
Field Location
 Soybean aphid on snap beans – not near alfalfa
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(viruses)
Thrips – no cabbage or onion near small grains
Colorado potato beetle – ¼ mile from last year’s
potatoes
Imported crucifer weevil on horseradish
Pepper fields away from corn to reduce corn borers
Plant away from dusty roads to reduce mite problems
(or control dust)
Plant leaf crops away from crops ready for harvest
(leafminers)
Asparagus fields away from alfalfa fields (plant bugs)
Field Selection
 Poorly drained soils increase root and seed
maggot problems
Tillage
 Corn root aphid
 Root and seed maggots (green and animal manure
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and crop residue)
Harlequin bug on crucifers (crop residue)
Diamondback moth and imported cabbageworm on
crucifers (crop residue)
Aphids on cabbage (crop residue)
Leafminers on leaf crops (crop residue)
Squash bugs (crop residue)
Squash vine borers (crop residue)
Fertilization
 Root and seed maggots (organic matter)
 Limit N use on leaf crops (aphids)
 Excessive organic matter increases damage
from springtails, symphylans and bulb mites
on leaf crops and bulb mites on onions
Weed Control
 Armyworm
 Stalk borer
 Cutworms
 Leafminers on spinach
 Stink bugs on tomato or peppers
 Eliminate grassy action sites for corn borers
 Flea beetles on crucifers and leaf crops (don’t
kill weeds during season)
Sanitation
 No cull piles of onions – onion maggot
 No cull piles of potatoes – Colorado potato
beetle
 Roguing and removing virus infected potato
plants (aphid vectors)
Trap Crops
 Colorado potato beetle (early or late)
 Early planted radishes as trap for flea beetles on
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other crucifers
Collards around cabbage for diamondback moth
control
Alfalfa planted near celery for plant bug control (don’t
mow alfalfa)
Squash bug and squash vine borer on squash and
pumpkin
Squash around muskmelons for striped cucumber
beetle control
Intercropping/Plant Diversity
 Cover crop or weeds between rows for
diamondback moth
 Cover crop or weeds between rows for
aphids on crucifers
Mulch
 Straw mulch for Colorado potato beetle
 Reflective mulches for aphids or thrips
 Black or clear mulch heats soil and reduces
seedcorn maggot and wireworm damage to
cucurbits
Barriers
 Row covers for many pests
 Plastic-lined trenches for Colorado potato
beetle
Irrigation
 Overhead irrigation for diamondback moth in
early evening disrupts moths mating and egglaying behavior
 Corn leaf aphid (avoid drought stress)
 Thrips on snap beans (avoid drought stress)
 False chinch bug on horseradish
Processing/Sorting
 Many pests of processed peas, sweet corn
and green beans – hand or electronic sorting
 Aphids on leaf crops – wash off with water
 Fruitworm damaged tomatoes or peppers –
visual inspection
Questions?