Cultural methods of suppressing insect and mite problems in the landscape include, soil preparation, choosing plants that are not attractive to pests or choosing plants that are tolerant of insects and diseases. Other ways to eliminate pests are by pruning or raking and then destroying infested plant residues. Irrigation can also reduce pest populations.

Soil Preparation
Providing a favorable soil environment will result in healthy plants which can resist pests and diseases. Applying fertilize and lime according to a soil analysis, allows plants to have access to all the necessary soil nutrients, and provides a suitable environment for earthworms and microorganisms. Supplement chemical fertilizers with organic material or compost to help ensure that all trace elements and major nutrients are available.

When using manure and compost, be sure they are worked into the soil. Otherwise, millipedes, white grubs, and other pests may be encouraged. Consider other means of adding organic matter, such as cover-cropping or mulching.

Till the soil in the fall to expose pests that live near the surface of the soil to natural enemies and weather, and to destroy insects in crop residues. If you do not till in the fall, do so early enough in the spring to give remaining vegetation time to decay before planting.

Plant Selection
Use disease and insect free, certified seeds and plants if available. Select plants that are sturdy and have well developed root systems. Diseases and insects in young seedlings may start in greenhouses or plant beds and cause heavy losses in the garden, i. e. whiteflies. Buy plants from a reputable grower who can assure you that they are disease and insect free. Avoid accepting plants from friends if there is any chance of also getting insects or diseases!

Plant cultivars that have insect resistance. Resistant cultivars are those which repel, are unattractive to, or otherwise are unsuitable as food for certain insects, or which will withstand feeding by certain pests with little reduction in yield or quality. Some cultivars may not taste as good to the pest. Some may possess certain physical or chemical properties which repel or discourage insect feeding or egg laying. Some may be able to support insect populations with no appreciable damage or alteration in quality or yield. Genetic engineering offers great potential for incorporating genes into plants that reduce their susceptibility to insect attacks.

By choosing plants carefully, gardeners can avoid some of the common pest problems. For example, a person wishing to plant hollies for landscaping could choose Chinese hollies instead of Japanese hollies, which are much more susceptible to southern red mites. If boxelder trees are desired, plant male trees rather than females to avoid problems with boxelder bugs, which feed on the seeds of boxelder trees and frequently enter dwellings to overwinter.

Rotation
Planting two similar crops in successive years tends to increase pest problems. Many vegetables are closely related and have the same pests. Some insects hibernate or lay eggs in or on the host plant. Do not grow the same kind of vegetable in the same place each year. Use related crops in a site only once every 3 or 4 years. Another type of crop rotation is to not follow root crops behind other root crops. Crop rotation is most effective on insects that develop on a limited number of plants.

Interplantings
Avoid placing all plants of one kind together; alternate groups of different plants within rows or patches. Insects that become severe on cabbage will probably also infect nearby mustard, broccoli, and collards. If an insect lays eggs, or otherwise attacks a specific species, the presence of unrelated plants in the area can interrupt progress of the attack by diluting the attractive odor of the preferred plants. This can also slow the spread of diseases and pests, giving the gardener more time to deal with them. Marigolds and garlic are two plants whose merits are frequently advocated as insect repellants, however, most of these claims have not been proven. In some cases the evidence indicates they are not effective.

Planting Dates
Some insects do not overwinter locally, but migrate from southern states each year. Time plantings in such a way that the majority of the crop will avoid the peak of insect infestations. Early squash should reach maturity before the pickleworm arrives; plant squash as early as possible to avoid borers, which lay eggs in July. Sweet corn planted early may avoid corn earworm, especially if harvested before July 15. By planting warm-weather crops after the soil has warmed, problems with seed and root rots will be avoided, and growth will be more vigorous. Keep a record of the dates insect problems occur.

Weed Control
Weeds and grasses can harbor both pest and/or beneficial insects. Spider mite problems are less if broadleaf weeds are controlled near fruit trees. If the weeds are closely related to the crop plants they will probably serve as a source of pest insects and should be removed. Pests with a wide host range such as armyworms, crickets, cutworms, flea beetles, grasshoppers, lygus bugs, slugs, snails, stink bugs, and thrips often inhabit weedy areas and can move to nearby desirable plants. It is best to mow weedy areas before the crop is planted and continue to do so on a regular basis. If you mow the weeds after the crop has become established, you may "force" the insects to move to the desirable plants.

Trap Crops
With this concept the gardener plants a crop that is very attractive to insects and then treats the trap crop rather than the crop the gardener is trying to grow. Soybeans, zinnias, or white roses can be used as trap crops for Japanese beetles. Radish, turnips, or mustard can be used to attract Harlequin bugs; radish attract corn and cabbage maggots; and sunflowers attract plant bugs.

Handpicking
Inspect plants for egg clusters, bean beetles, caterpillars, and other insects. Handpick as many as possible. If you don't like squashing the pests, knock the insects and egg clusters into a coffee can or quart jar with a small amount of water and then pour boiling water over them. Kerosene is often recommended, but poses a disposal problem once you have finished; besides, water is cheaper.

Traps
Insect traps are used for detection and management purposes. Light traps, particularly blacklight or bluelight traps (emit ultraviolet light that is highly attractive to nocturnal insects), are good insect-monitoring tools, but provide little or no protection for the garden. While they usually capture a tremendous number of insects, a close examination of light trap collections shows that they attract both beneficial and harmful insects that would ordinarily not be found in that area. Those insects attracted, but not captured remain in the area, and the destructive ones may cause damage. Also, some wingless species as well as those species only active during the day (diurnal, as opposed to nocturnal) are not caught in these traps. Consequently, the use of a light trap in protecting the home garden is generally of little benefit and, in some instances, detrimental. They can be helpful to detect when a pest has become active or moves into an area.

Pheromone traps are for detection or sometimes for disrupting mating habits of insects. The female produces and releases a chemical odor attractive to male insects of the same species. The male can detect the odor at low concentrations. The effectiveness of lures are reduced by rainfall, cool temperatures, and wind speed and direction. The scented lures can be damaged by heat or sunlight in shipment or during storage before they are used. Limited success has been achieved in insect control using pheromone traps. The best success has been achieved when the pest density is low and movement into the area is minimal. Pheromone traps can best be used as a method of monitoring the presence of some insects.

A simple Japanese beetle trap can be made from a single milk jug and a plastic bag. The bait used to attract the beetles is available at most farm and garden supply centers. Place traps away from desirable plants or you may increase plant damage. A shallow tin of beer partially embedded in the soil can make an effective trap for slugs. Yellow plastic dish pans filled with soapy water may be used to attract aphids. White flies and cucumber beetles can be caught with yellow sticky traps, made with boards painted yellow and lightly coated with oil or grease. Commercial sticky traps are available through some catalogs.

Barriers
Mechanical barriers are most effective when aimed at excluding one or a few pests rather than all pest. Aluminum foil and other reflective mulch has been shown to repel aphids. However, the environmental impact and energy consumption involved in making aluminum foil deserves consideration. Crushed eggshells or hydrated lime spread around plants will discourage slugs. While heavy mulch is good for weed control, it gives slugs a place to hide.

Collars made of cardboard, tin cans, or aluminum foil are effective barriers to cutworms. When placed around seedlings and inserted about halfway into the soil, collars prevent cutworms from moving to seedlings stems. Use of screening around potato storage areas can prevent the entry of tuberworm moths. Mounding soil around grape vines can prevent the emergence of grape root borer moths. Paper bags can be used to cover ears of corn to keep birds and insects out (do not cover until pollination is complete).

Net-covered cages over young seedlings will help prevent insect, bird, and rabbit damage. Cheesecloth screens for cold frames and hot beds will prevent insect egg laying. Floating row covers of spun polyethylene are a little more expensive, but their effectiveness in excluding insects is proven by the number of commercial growers that use them, particularly on cole crops and strawberries. Sticky barriers on the trunks of trees and woody shrubs will prevent damage from some crawling insects.

Pruning, Raking
Some pests, such as the azalea stem borer and the dogwood twig borer, can be controlled by pruning infected twigs out of infested plants and destroying them. If infested twigs are pruned in late spring or early summer, these plants should bloom without any problem the following spring. However, if infested twigs are pruned out in late summer, a larger portion of the branch must be removed (the larvae bore downward inside the stem), and the plant will not have time to set new flower buds before winter. The fallen twigs of pecans, oaks, elms, hickories and other shade trees should be raked up in the fall to destroy the larvae of twig girdlers. These longhorned beetles overwinter as eggs or grubs in fallen twigs. New beetles emerge during the following fall to lay eggs in and chew off more twigs.

Irrigation
Spraying infested plants with a strong stream of water dislodges and kills many spider mites, aphids, and other relatively fragile insects. Rain is one of the greatest natural control factors for spider mites; populations tend to build up during dry weather. Irrigation of turf is helpful in managing chinch bugs, spider mites, aphids, and other pests that are susceptible to the fungal diseases which are promoted by high humidity.

Consumer Horticulture | Quick Reference

© Erv Evans, Consumer Horticulturist
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