Insect Control in the Organic Vegetable Garden
Outline
• Planning to avoid pests
• Insect Monitoring and Identification
• Fundamentals of Organic Insect Control
– Cultural Practices
– Sanitation, exclusion
– Attracting natural enemies
– Botanical and biological pesticides
• Key vegetable insect pests and control
strategies
Organic Control ‘Toolbox’
Example for Cucumber Beetle
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Source: Univ. of Kentucky Entomology
Habitat for natural enemies
Grow cucurbit varieties less attractive
to beetles
Long distance crop rotation
Transplant vs direct seeding
Eliminate crop residues
Manipulate planting date (may miss
peak markets)
Row covers (may interfere with
weeding)
Mulch (may exacerbate other pests)
Trellis plants (labor)
Trap crops, baits and sticky traps
(labor, cost)
Approved materials
– Neem, Beauveria bassiana, kaolin
clay, pyrethrin, spinosad
First Steps
Manage Soil for Healthy Plants
• Soil test (pH, P, K,
micronutrients)
• Organic matter (cover
crops, compost)
• Fertility plan
– Application based on
crop needs
• Avoid excess N
• If planting in turf
– Till before planting
– Check for grubs
Choose Less Susceptible
Varieties
• Hairy-leaf varieties
• Tight husked corn
– Corn earworm
• Virus-resistance
– GMO
– Tomatoes
– Cucurbits
• Squash vine borer
– ATTRA publication
Avoid Pest Insects in Time
Gather info on key pests
• Early planted crops
generally have lower
insect pressure
– Pests with multiple
generations
– Stink bugs, whiteflies,
tomato fruitworm
– Don’t prolong harvest
• Late planting
– Pests that overwinter
locally
– Cucumber beetles, bean
leaf beetles
Harvest before early July
to avoid Pickleworm
Avoid Insect Pests in Space
Garden Layout Plan (learn crop families)
• Rotate beds/plots to
different plant families
• Avoid successive
plantings of same
crop in adjacent beds
• Maximize diversity
– Interplanting
– Mix different families
– Add flowering plants
Keeping Records
Sampling Scheme
• Begin sampling at planting
• Sample weekly by crop
• Sample enough plants to
represent planting area, and
that can be done in a
reasonable time
• Records will document
what’s present, and whether
populations are increasing,
or decreasing
Sampling Equipment
To Spray or Not to Spray
• Keep organic insecticides handy
– Purchased, home-made
• Decision to spray based on
– Experience
– Insect’s potential for damage
• Type of damage (direct or indirect)
– Stage of plant growth
– Population trends (sampling records)
– Does insect have natural enemies; are they
present?
Evidence of Natural Enemies
Plants Can Tolerate Some Defoliation
Example: Potatoes
Plant Growth
Stage
Maximum
Defoliation
Without Yield Loss
Plant emergence
to early bloom
20%
Early bloom
30%
Late bloom till
harvest
60%
Insect Identification
ID insects at least to Order, and if possible to Family
Classification
Kingdom -- Animal
Phylum -- Arthropoda
Class -- Hexapoda (= insects)
Order -- Lepidoptera (= butterflies and moths)
Family -- Noctuidae (= noctuids)
Genus -- Helicoverpa
Species -- Helicoverpa armigera (Tomato
fruitworm, corn earworm
Key Insect Orders
Orthoptera: Grasshoppers
and Crickets
Hemiptera: True Bugs
Thysanoptera: Thrips
Key Insect Orders
Coleoptera: Beetles
Diptera: Flies
Key Insect Orders
Homptera: Aphids,
whiteflies
Lepidoptera: Butterflies,
moths
Hymenoptera: Ants,
bees, wasps
Arachnids: Mites and Spiders
Spider mites
Spiders
Insect Metamorphosis
Incomplete (12%)
•Grasshoppers
•True bugs
•Aphids, thrips
Complete (88%)
•Beetles
•Flies
•Ants, wasps, bees
Tips to Identify Larvae
Lepidpotera
(Caterpillars)
Coleoptera:
Beetles
Tips to Identify Larvae
Hymenoptera:
Wasps
Diptera: Flies
Quiz: What are these?
Hint: One on top will undergo complete metamorphosis;
One on bottom; incomplete metamorphosis
Cultural Practices
Tillage
• Disrupts insect pest
life cycles
• Exposes them to
weather, predators
• Destroys crop debris
• Accelerates organic
matter decomposition
• Depletes food for
microbes
• Degrades soil structure,
erosion
Mulches
Organic
• Straw mulch
– Retains soil moisture,
lowers soil
temperature
– Habitat for predators
(and some pests)
– Excellent for potatoes,
cucurbits
Mulches
Plastic
• Black
– Speeds early season
crop growth
• Reflective:
– Repels thrips, aphids
– Reduces spread of
viruses
Melon-Virus Experiments
Cover crop as camouflage
• Annual rye planted
between rows in late
fall
• Virus incidence lower
in cover crop
treatments
• Reflective mulch also
reduced virus
incidence
100
Cover
No Cover
50
0
2003
2004
% Plants Infected with WMV
Sanitation
• Start with pest free
transplants
• Remove crop residue
after harvest
• Remove diseased
plants
• Remove weeds
– Establish perennial
and flowering plants
for natural enemy
habitat
Exclusion
High Pressure Spray
(Aphids, mites, whiteflies)
Water Wand: Cecil Stokes; E-mail (theroseman@gbronline.com)
Attracting Natural Enemies
Making use of Nature’s Services
• Use of hedgerows in
farming
– Small trees, shrubs
– Perennial grasses,
forbs
– Flowering annuals
• Begin growing before
crop
• Provide food and
shelter for natural
enemies
Attracting Natural Enemies
Insectary Plants in the Garden
• Establish insectary
border(s)
– Pick plants for
successive bloom
spring-fall
– Fruit trees, flowering
shrubs, perennial and
annual flowers
– Include low growing
plants (ground
beetles)
Insectary Plants
• Apiaceae (small
parasitic wasps)
– Fennel, coriander, dill,
wild carrot
• Compositacae/Asteraceae,
mint family (predatory
wasps and flies)
– Daisy, chamomile,
zinnia, echinacea,
spearmint, catnip
• Thyme, rosemary, clover
– Bees, wasps, ground
beetles
Some Organic Insecticides
• Entrust (Spinosad)
– Microbial fermentation
product
– Targets: caterpillars,
thrips, leafminers, some
beetles
– Soft on natural enemies,
but toxic to bees
– $550/lb
• 1 gram/5 gal
• 450 tanks = $1.20 each
Bacillus thuringiensis
– BT kurstaki and
aizawai
• Controls caterpillars
– BT israelensis
• Mosquito larvae
– BT tenebrionis
• Beetle larvae
– Insects must eat
treated foliage
• Good spray coverage
– Better against small
larvae
Neem
• Azadirachtin: extract
from neem tree
• Multiple modes of
action, including
repellency
• Broad spectrum
– Best against larvae
– Also good on
whiteflies,aphids
Pyrethrin or Pyrethrum
• Extract from flowers
of pyrethrum daisy
• Broad spectrum
• Breaks down quickly
Insecticidal Soap
• Potassium salts of
fatty acids
• Acts by smothering
and can break down
insect cuticle
• Best against soft
bodied insects
(aphids, whiteflies,
mites)
Kaolin Clay
• Applied as a slurry
before pests arrive
• Physical barrier,
deterrent, irritant
• Mix well, remove
sprayer filter
• Must wash fruit
Pepper and Garlic Sprays
BT Garlic Pepper Karate Neem Control
Cucurbit Pests
Squash Bug Control
• Crop rotation and sanitation are very important. Rotate next years
crop to different area.
• During the summer, adults tend to congregate under shelter at night.
Place boards on the soil surface near the squash in the evening and
the next morning collect and destroy the pest.
• Destroy egg masses on the underside of leaves.
• A parasitic fly, Trichopoda pennipes, affects adult squash bugs and
several wasps parastize the eggs. Provide habitat for these in or
near the field.
• If squash bugs are a problem on your farm, avoid heavy mulch or
no-till in susceptible crops such as zucchini. Squash bugs like
shelter, and appear more numerous in reduced tillage or mulched
crop systems.
• Pyrethrin and Neem products
Cucurbit Pests
Squash Vine Borer Control
• Winter squash, pumpkins and zucchini are particularly
susceptible. Butternut squash (C. moschata) is resistant.
• Soon after crop harvest, plow the vine debris deeply to
bury over larvae.
• Rotate fields.
• In small plantings, it may be possible to manually
remove the larvae. Find the sawdust-like frass on the
affected plant stem, and then locate the larva by slicing
lengthwise along the stem until you reach it. Destroy the
larva, and then cover the slit stem area with soil.
• Keep floating row covers in place after transplanting or
direct seeding until flowering.
Cucurbit Pests
Cucumber Beetle Control
• Crop rotation and sanitation are important.
• Floating row covers are very effective for avoiding beetle damage.
Remember to temporarily remove the covers periodically to weed
early, and leave off permanently when the flowers appear to allow
pollination.
• Use of trap crops. Cultivars vary dramatically in their attractiveness
to beetles. The inexpensive variety Dark Green Zucchini and Blue
Hubbard squash are effective trap crops.
• Yellow sticky cups or tape can trap adults. They should be replaced
regularly as they become saturated with beetles and field debris.
• Use transplants instead of direct seeding. They will be older when
beetles arrive and therefore more tolerant, or you can plant later
after peak beetle activity is over.
Solanaceous Crop Pests
CPB Control
• Crop rotation
• Propane flamer; young potato plants if infested
• Mulch crops with straw or hay before adults
arrive
• Hand picking
• Entrust, Neem
Solanaceous Crop Pests
Flea Beetle Control
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Row covers
Spinosad
Neem products
Capsaicin gives some control (45% in one study). The
product, Miller’s Hot Sauce™ is OMRI-approved and labeled
for use on crop plants as a mammal repellant. If so used, it
will also reduce flea beetle damage.
• Pyrethrum: Pyganic™ has shown variable results
• Kaolin clay (Surround™).
Sweet Corn Pests
Corn Earworm Control
• Corn varieties with long, tight husks impede the entrance of
the worm somewhat, but these provide only partial control.
Varieties that have been reported to be less susceptible to
damage include: Silver Queen, Stowell’s Evergreen, Viking
RB, Supersweet JRB, Golden Bantam, Jubilee, Texas Honey
June, and Bodacious.
• Since the pest is usually not a problem until mid to late
summer, planting early to schedule harvest before expected
arrival of CEW and using short season varieties will help
avoid injury.
• BT and oil (Zea-Later); apply when silks reach full length
• Spinosad
Questions
zehnder@clemson.edu