Once insect problems have begun in the organic garden, what can be done to control them? When insect numbers are high, injury may be reduced but is seldom eliminated by non-chemical methods. Physical barriers, such as collars placed around young plants, will help protect against cutworms. Trapping methods, such as the use of flat boards or shingles placed on the ground near plants, will attract pests such as slugs, snails, and squash bugs in search of darkness, moisture, and protection. Here they can be collected and destroyed. Reduce spidermite populations on some plants by syringing the foliage with water or by hosing down the plant with a strong force of water.
Floating row covers consisting of lightweight, fine-meshed fabric can be loosely draped over crop rows and anchored to the soil at the edges. The small mesh size excludes nearly all insects the size of aphids or larger. Row covers provide the greatest amount of protection if applied before insects become a problem. Row covers also extend the growing season and moderate harsh summer temperatures. For crops that require insect pollination, such as squashes, cucumbers and melons, or that benefit from insect pollination, like eggplants, lima beans, okra and peppers, row covers should be removed once flowering begins.
Natural populations of predators and parasites are valuable for reducing infestations of garden pests. Usually, however, some level of pest infestation must be tolerated to attract and maintain natural enemy populations. Should pest control be necessary, select a management strategy that will conserve or minimize injury to beneficial insects, while attaining satisfactory control of the target pest. Several species of mass-reared beneficial insects can be purchased from commercial suppliers for use in home gardens, however, the artificial introduction of natural enemies usually does little good in the home garden because the insects often die or disperse into areas outside the garden. It is probably more productive to provide good conditions for natural beneficial insect populations to increase than to introduce exotics.
There are a few products that have insecticidal properties that may be acceptable to organic gardeners since they are not synthetically derived. However, most of these materials will kill beneficial insects as well as the target pest.
- Bacillus thuringiensis- commonly refered to as B.T. and marketed under the trades names Dipel, Thuricide and others. Consists of spores from a soil-inhabiting bacteria that kills the larvae of moths and butterflies.
- Rotenone- a non-synthetic insecticide derived from the roots of a certain plant. Most effective of the non-synthetic insecticides but residual activity is very short.
- Sulfur- finely ground sulfur can be used either as a dust or spray to control spidermites. The chemical may ‘burn’ tender foliage if air temperature is 90 degrees F or higher.
- Insecticidal soaps- effective at controlling some soft-bodied insects such as aphids, mites, leafhoppers and plant bugs. Requires thorough plant coverage and multiple applications. Use soaps with caution, as leaf injury is possible with certain plants.
Sarah Browning is an Extension Educator with the University of Nebraska- Lincoln Extension in Dodge and Saunders Counties. She can be contacted by phone at 727-2775: by mail at 1206 W. 23rd Street, Fremont, NE 68025: or by e-mail at sbrowning2@unl.edu
