Insect pest control, especially in the vegetable garden, is more complicated than it used to be because of concern about persistent pesticides.  Many of the old standbys are no longer allowed in the vegetable garden for the simple reason that they last too long.

Why do we have so many insect pests, anyway?  Our typically mild winter climate presents a mixed blessing.  While it allows us to grow something in the garden nearly year-round, it also allows many insect pests to live through the winter season that might otherwise not survive if a long, cold spell occurred.  With the past winter being unusually mild - thanks in part to El Nino - we can expect insect pests to be persistent adversaries during the late spring and summer season.

When we plant a garden, we change a lot of Mother Nature's ideas about ecology in part by reducing the diversity of plant types in a given area.  For instance, in nature a single plant species does not grow naturally in a row.  Growing a single plant variety (which is typically very uniform genetically) in a limited area tends to favor the buildup of those insect pests that attack the plant.

Today's favorite garden varieties have been developed primarily for flavor and texture.  Insect-resistance is great but no one is willing to eat lettuce if it looks like it has been used for target practice or has the taste and texture of leather.

Because we've become so accustomed to having good quality vegetables, it's difficult for most of us to accept insect-damaged vegetable.  Although pesticides have done an admirable job of controlling most pests, most of the time, the use of as many non-toxic or low-toxic organic controls as possible is certainly justified.

The following recommendations range from non-toxic to low-toxic and should help to shift the balance of nature in your favor as you deal with insect pest problems this season.  Many also have applications for insect problems on fruit trees and landscape plants.

HAND-PICKING. Certainly not for the timid or squeamish, but very effective against larger-sized insect pests and particularly if you start early in the season. Tomato hornworms, squash bugs, stink bugs and other beetles can be effectively controlled in small areas by periodic removal and subsequent dunkings in a can of diesel or by applying sufficient pressure to the pest against an immovable object with the sole of your shoe.

WATER SPRAYS. On sturdy-type plants, high pressure streams of water are safe and effective in reducing numbers of small insects like aphids and mites. Just give the plants a good shower bath periodically, being certain to direct the spray to the underside of the leaves as well as to the top. When so dislodged, most aphids and spider mites fail to return to plants. However, if insect populations start to get out of hand, consider utilizing an organic insecticide.

B.t. Insects have diseases just like people do. One of these, Bacillus thuringiensis, can be very effectively used to control many types of caterpillar larvae, such as armyworms, webworms, loopers and hornworms. After such larvae eat it, they stop feeding almost immediately and become ill and then die. It is widely available under a variety of trade names such as DIPEL, B. T. BIOSPRAY, BIO-WORM KILLER, etc.

Try to spray this material in the evening or early morning because it is broken down by ultraviolet light. Best of all, this preparation is non-toxic to other animals including bees and other beneficial insects.

ROTENONE. This is a plant-derived insecticide that is effective on a variety of insects including thrips and many types of beetles. Rotenone is extracted from several tropical plants. It is also present in a native weed known as Devil's shoestring which American Indians used as a fish poison.

INSECTICIDAL SOAP. This organic insecticide is very effective against many types of insect pests. In fact, various types of soap formulations have been used by gardeners to control insects since the early 1800's. Safer's Insecticidal Soap is registered for use on edible crops and is widely available. It controls such pests as spider mites, aphids, mealybugs, whiteflies, harlequin bugs, stink bugs and thrips.

PYRETHRUM. This is a botanical insecticide derived from a species of Chrysanthemum. Pyrethrum causes rapid paralysis of most insects but they usually recover unless the pyrethrum is used in combination with a synergist or other poison such as piperonyl butoxide to enhance the toxicity level. This combination of insecticides is often used in household sprays, space foggers and wasp and hornet sprays.

Regardless of whether your chemical attack is synthetic or organic, always be sure to treat all insecticide with utmost caution and follow the manufacturer's directions.



This web site is maintained by Master Gardener Laura Bellmore, under the direction of William M. Johnson, Ph.D., County Extension Agent-Horticulture & Master Gardener Program Coordinator.

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