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CONTROLS FOR GREENHOUSE VEGETABLE INSECT PESTS
Ricardo T. Bessin and Lee Townsend, Extension Entomologists
University of Kentucky Department of Entomology
The warm humid conditions and abundant food in the greenhouse are ideal for
pest build up. Problems can be chronic unless recognized and corrected. While insecticides
are important tools, successful control of greenhouse vegetables pests relies primarily on
cultural factors. Proper cultural practices can minimize the chance for initiation and build up
of infestations. Early detection and diagnosis are key to greenhouse pest management, as well
as, the proper choice and application of pesticides when pest outbreaks occur.
CULTURAL CONTROLS
Pests may enter the greenhouse in the summer when the ventilators are open.
Others may be brought into the greenhouse on new plant material or in soil. Many are able
to survive short periods of time between harvest or plant removal and production of the next
crop. Cultural controls are the primary defense against infestation.
- Proper cultural practices which will help prevent pest
infestations include:
- Maintain a clean, closely mowed area around the greenhouse to
reduce pests that develop in rank growth.
- Remove all plants and any plant debris, clean the greenhouse thoroughly after each
production cycle.
- Keep doors, screens and ventilators in good repair.
- Use clean or sterile soils or ground media, tools, flats and other equipment.
- At the conclusion of the season remove all plants and any plant debris, clean
greenhouse thoroughly and fumigate.
- Inspect new plants thoroughly to prevent introduction insect or disease infested
material into the greenhouse.
- Watch for leaks or pooled water that can lead to fungus gnat infestations.
- If possible allow the greenhouse to freeze in winter to eliminate tender insects like
whiteflies.
- Avoid wearing yellow clothing which is attractive to many insect pests.
- Eliminate infestations by discarding or removing heavily infested material.
MONITORING
Early detection and diagnosis of pest infestations will allow you to make pest
control decisions before the problem gets out of hand. It is good practice, therefore, to make
weekly inspections of plants in all sections of the greenhouse.
Insect monitoring devices are also available. Yellow stick cards (PT Insect
Monitoring & Trapping System, Whitmire) are highly attractive to winged aphids, leafminer
adults, whiteflies, leafhoppers, thrips (blue cards can also be used with thrips), various flies
and other insects. These can be used to alert you to the presence of a pest and identify hot
spots in the greenhouse. One to three cards per 1000 sq. ft. in the greenhouse is
recommended and should be changed weekly. If you cannot identify a trapped insect, contact
your county extension agent for assistance. Mass trapping products such as sticky tapes are
also available for thrips, whitefly, leafminer and fungus gnat detection and management.
| INSECTICIDE OR BIOLOGICAL CONTROL | REGISTERED GREENHOUSE CROPS | INSECTS AND MITES CONTROLLED |
|---|
| Bacillus thuringiensis | All crops | Armyworms, cabbage loopers, hornworms, cutworms, green cloverworms, salt marsh caterpillars, tomato fruitworm. |
| Comments:
A microbial insecticide effective against several species of caterpillars.
This must be ingested by the insect to be effective. After eating a lethal
dose, larvae stop feeding within the hour and will die within several days. |
| Encarsia formosa | All crops | Whitefly management |
| Comments:
A tiny wasp parasite which attacks whiteflies in greenhouses. While
they are not useful in controlling heavy whitefly infestations, they
can be used successfully against limited infestations under conditions
that favor their development over development of whiteflies (64°- 80°F).
Parasitized larvae die and turn black, a parasite wasp will emerge and
continue the beneficial process. Do not throw pruned leaves away without
checking them for black parasite scales. Leave these under plants for
about 1 week until wasps have emerged. Very susceptible to insecticides.
More effective in controlling greenhouse whitefly than sweet potato
whitefly. |
| Endosulfan (Thiodan)(2 day PHI*) | Tomatoes only | Aphids, armyworms,
. blister beetles, cabbage
looper, colorado potato
beetle, flea beetles,
tomato fruitworm and
whiteflies. |
| Comments:
Wear a mask or respirator approved by MSA or OSHA for protection against
endosulfan. A foliar insecticide that is effective at higher greenhouse
temperatures. |
| Insecticidal soap | All crops | Aphids, leafhoppers,
plant bugs, spider
mites, thrips and
whiteflies. |
| Comments:
Apply when insects first appear. Contains potassium salts of fatty acids.
Kills on contact and is neither a stomach nor a residual poison.
Exempt from tolerances, can be applied just before harvest. |
| Malathion | Cucumbers(1 day PHI), Endive (7 day PHI), Lettuce (14 day PHI), Radish (7 day PHI),Tomatoes (1 day PHI) | Aphids, armyworms,
cabbage loopers,
cutworms, fruit flies,
garden fleahoppers,
mealbugs, serpentine
leafminers, spider
mites, thrips and
whiteflies. |
| Comments:
A organophosphate insecticide with broad spectrum activity. Spray
plants thoroughly. Do not apply unless plants are dry.
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| Metaldehyde | On and beneath greenhouse benches | Snails and slugs |
| Comments:
Pellets containing 2.75% metaldehyde (HACO, Inc.) Do not allow pellets
to come in contact with plants. Thoroughly wet area before and after
pellets are spread. |
| Pyrethrin + Piperonyl Butoxide (Pyrenone Crop Spray, Pyronyl Crop Spray) | All crops | Aphids, armyworms,
cabbage loopers,
caterpillars, colorado
potato beetle, cucumber
beetles, flea beetles, fruit
flies, leafhoppers, mealy-
bugs, thrips, spider mites,
tomato fruitworm and
whiteflies. |
| Comments:
Apply when insects first appear. A botanical insecticide that is
especially effective against whiteflies. For best results, apply
during the early evening when foliage is dry and air temperature
is between 60-80°F. Effectiveness is enhanced when in combination with
the synergist, Piperonyl Butoxide. Available as sprays and total
release aerosols. |
| Bacillus thuringiensis israelensis (Gnatrol) | Tomatoes, leafy and cole crops, cucumbers, peppers, eggplants. | Fungus gnat larvae. |
| Comments:
Must be timed for a stage of development when larvae are present in
the soil. |
| *PHI = Mandatory pre-harvest interval. |
Revised: 1/04
CAUTION! Pesticide recommendations in this publication
are registered for use in Kentucky, USA ONLY! The use of some products
may not be legal in your state or country. Please check with your local county
agent or
regulatory official before using any pesticide mentioned in this publication.
Of course,
ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY
PESTICIDE!
This page is maintained by Pat Dillon, Department of Entomology, University of Kentucky.
Please send questions or suggestions to: pdillon@uky.edu
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