Insect Note #17 (Revised)
Prepared by:
Kenneth A. Sorensen, Extension Entomologist, NCSU
Dated 10/93
Placed on the Web 4/95 by the Department of Entomology, NCSU
Revised: 3/05
Greenhouse Vegetable Insect Control
Tomatoes, lettuce and cucumbers are the main vegetables grown in
plastic or glass greenhouses in North Carolina. However, onions,
spinach and radish are also grown. As we create a favorable
environment in the greenhouse for growing tomatoes, cucumber,
lettuce and other vegetables, we also create a favorable habitat
for their insect pests. Under greenhouse conditions, which are
void of natural forces that often keep insects under control
(weather, natural predators and parasites), insects have the
capacity to reproduce rapidly and cause extensive damage.
Insects and mites constantly threaten greenhouse vegetable growers.
Sometimes these pests inflict real damage and economic losses, and
other times they are simply just a plain nuisance. At least 30
species of insects, mites, slugs, and symphylids feed on the
foliage, fruits, stems, roots, or attack seedlings of vegetables
grown in greenhouses.
- On tomatoes, the most common insect problems are aphids,
whiteflies, leafminers and tomato pinworms. Other insect pests are
armyworms, tomato fruitworm and cabbage looper. Spider mites also
can be a problem under hot, dry conditions. Insects are most
destructive in the fall when field populations are high and they
migrate to houses before covers are added or openings are screened
or closed.
- Aphids and leafminers, in addition to their damage by feeding
can spread some tomato diseases and/or provide infestation sites
for others. Aphid-borne virus infection from surrounding
vegetation and gardens is the principal reason for crop failures in
the fall of the year. Great care must be taken to eliminate aphids
and other insects close to the greenhouse (at least 100 feet).
- The various caterpillars (especially loopers, armyworms and
fruitworms), once established, can cause tremendous damage to
foliage. Prevention of their entrance to the greenhouse is most
important. This can be done by screens and proper installation of
exhaust fans in houses that are fully covered.
- On cucumbers, the most common insect pests are aphids,
cucumber beetles, leafminers and spider mites. As with tomatoes,
these insects can be vectors of disease organisms in addition to
their feeding activity.
- On lettuce, aphids and cabbage loopers are most
troublesome. Cutworms, whiteflies, leafminers and slugs are
sometimes abundant enough to cause economic concern.
A well-planned, properly administered management program can
frequently prevent damaging populations of insects and keep levels
under control. Prevention is most important! Sanitation, screened
openings, insect-free transplants, daily inspection of plants and
isolation are important considerations in greenhouse pest control.
Obviously, crop husbandry and stewardship will favor plant growth
over insect establishment and development. Separate plant houses
and considerable distance of houses from outside growing areas such
as gardens will help avoid unnecessary contamination. A complete
cleanup between crops is also recommended.
The effective use of biological control is possible and encouraged.
The use of yellow sticky traps helps keep adult whiteflies and
aphids in check and monitors their movement and development in
concert with the use of Encarsia formosa against the
whitefly, Phytoseilus persimilis against the spider mite and
Diglyphus isaea against leafminers. The introduction of
lady beetles, lacewings or midges for aphids, the use of plastic as
a ground cover for thrips and the use of Bacillus
thuringiensis for worms offers additional tactics in the battle
against bugs in the greenhouse. Regular and frequent inspections
of plants for pests and beneficials and good record keeping are
essential to pest management.
Environmental management can also influence pest development in the
greenhouse. Temperatures above 85 degrees F and below 60 degrees F slows the
development of pests and gives parasites an advantage. High and
low relative humidity also slows the development of certain pests.
Likewise, the misting of foliage during the day will dislodge
aphids, leafminer adults and adult whiteflies. The timely use of
ventilation fans or the constant use of circulating fans and the
use of airblast sprays also discourages the settlement of adult
whiteflies and leafminer adults in the tops of plants. Obviously,
extreme high or low temperatures between crops will kill certain
pests stages. High levels of CO2 also inhibits insect
development.
The decision as to the necessity of control must be based on insect
and mite species involved, type and location of feeding on a
particular crop, age of plant, amount of damage caused by given
numbers of pest, and the potential for disease infection.
Always remember, however, that it is essential to identify the pest
properly before using any pesticide. Since some
insecticidal formulations for use in greenhouses are not readily
available in some areas, plan ahead so that you will have on hand
the proper materials when needed.
General Precautions and Comments Regarding Pesticides
- Pesticides are poisons, and any pesticide will be toxic to man
if enough of the material is inhaled, swallowed, or absorbed
through the skin. However, some are much more dangerous to use
than others. There are various ways of measuring toxicity of
chemicals, but one of the most practical ways for the user to
determine the toxicity of a marterial is by reading the label.
Labels that display a SKULL and CROSSBONES with the worlds "DANGER-
POISON" in red are highlyl toxic and must be handled with extreme
caution. Labels with the word "WARNING" are moderately toxic, and
those with "CAUTION" are the less toxic materials. All labels must
list precautions to take before, during, and after applying the
material. Therefore, before using any material, take the time to
read the label, and follow the instructions given. Labels
are printed to protect the user, the consumer, and the
environment.
- Stores pesticides in closed, well-labelled containers away from
heaters. Do not leave the materials in the open where children or
customers may accidentally come in contact with them.
- Store application equipment as you do pesticides--out of reach
of children or pets. Avoid, if possible, the use of equipment in
which herbicides have been used.
- Do not save or reuse empty pesticide containers. Rinse,
puncture and dispose of them in a safe manner. Recycling empty
containers is available in many areas.
- Do not apply more pesticide than the label recommends.
Overdosage is wasteful or may cause plant damage. Also, excessive
residues may occur and the crop may be confiscated.
- If you use poison bait to control rats, mice or other pests,
either indoors or outdoors, place it where children or pest cannot
find it.
- When opening a container of liquid pesticide, keep your face
away from and to one side of the cap or lid. Wear the necessary
protective clothing.
- Mix or prepare dusts or sprays outdoors or in a well-ventilated
room.
- In handling any pesticide, avoid contact with the skin. Do not
get it near your mouth, eyes, or nose.
- If pesticides get in your eyes, flush the eyes with water by
hand or at an eye wash station immediately, continue for 15
minutes, and seek medical attention.
- Never smoke, eat, or drink while handling pesticides. After
finishing work, wash exposed skin surfaces with soap and water.
- If you spill a pesticide on your clothing immediately remove
clothing and take a shower or bath.
- If you become ill during or shortly after using a pesticide,
call a physican immediately. From the container label, read to him
the names of the active chemical ingredients; follow his
instructions for first aid treatment.
- Since a greenhouse is a permanent installation, keep the
following Poison Control Center and telephone number posted at all
times.
STATE-DESIGNATED POISON CENTER
1-800-848-6946 (1-800-84-TOXIN)
Carolinas Poison Center
Carolinas Medical Center
P.O. Box 32861
Charlotte, NC 28232-1020
GREENSBORO
1-800-953-4001
Triad Poison Center, Moses Cone Hospital
1200 N. Elm Street
Greensboro, NC 27401-1020
WILMINGTON
1-910-343-7046
Poison Control Center
2131 S. 17th Street
Wilmington, NC 28401
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- With more and more organophosphorus compounds being recommended
and used in the control of greenhouse pests, it is essential that
proper and efficient protective respiratory devices be worn by
workers handling these insecticides.
- Post signs with date of treatment and reentry.
The use of brand names and any mention or listing of commercial products or
services in this publication does not imply endorsements by the North Carolina
Cooperative Extension Service nor discrimination against similar products or
services not mentioned. All pesticide recommendations provided in this
publication apply to pest control in North Carolina. Individuals who use
chemicals are responsible for ensuring that the intended use complies with
current regulations and conforms to the product label. Be sure to obtain
information about product usage in your locale and examine a current product
label before applying any chemical. The information presented on pest
biology is based on conditions in North Carolina and may not be applicable
to your locale. For further information, we recommend that you contact the
Cooperative Extension Service office in your county.
