oc rA24S.7 B-1300 1 Texas Agricultural Extension Service 11 -98 73 ._0UViI•.• Texas A&M University System ).1300 LIBRARY TEXAS A&M- UNIVE'RSITY MA~ 29 1999 H:J<A6 STATE DOCUMENTS TEXAS STATE DEPOSI AY afld(/tfl(/ , .Insect and, Mite,. Pests in Vegetable Gardens John A. Jackman Professor and Extension Entomologist The Texas A&M University System Texas Agricultural Extension Service· Chester p, Fehlis, Deputy Director· The Texas A&M University System • College Station, Texas (Blank Page in O.... IIBUUetiBJ . t . ~ :.' ", ~ ~ " k · . ;.,' Managing Insect and Mite Pests in Vegetable Gardens egetable gardening is an enjoyable pastime. the surface of a leaf when feeding, while the same The resul t of your labors is fresh, home- caterpillar may eat great chunks of leaves when V grown produce. Frequently, growing your mature. own vegetables is even less expensive than buying An insect's mouthparts can be a key to under- not-so-fresh produce from the market. standing the type of damage caused by a pest. However, producing your own vegetables can be Insects with sucking mouthparts feed by piercing challenging. One of the greatest challenges is to suc- leaves or fruit. Damage appears ~s pock marks or cessfully control insect pests. Fortunately, there are mottled leaves. Insects with chewing mouthparts numerous management alternatives that vegetable chew holes in plants. If you can recognize the type gardeners may consider when dealing with insects of feeding, you can select the proper insecticides and other pests. These include cultural, biological, (i.e., stomach poisons for chewing insects). and management controls and, last but not least, chemical controls. Plan ahead Understanding insects When planning a vegetable garden, anticipate the pests that may occur during the year. Consider all There are approximately 30,000 insect species in management practices that will help deal with the Texas. Fortunately, fewer than 100 species are rou- pests before they become problems. Then, develop a tine pests in vegetable gardens. Most insects found management plan and put it into use before prob- in gardens are either incidental or beneficial, con- lems occur. Use your past experience as a guide in tributing to pollination, the balance of nature, or anticipating pests for the upcoming season. recycling of organic matter. A garden with an abun- dant supply of insects actually may be quite healthy Integrated Pest Management and productive. However, insect pests can reduce the quantity or quality of the vegetables produced Integrated pest management, IPM, is a philoso- and may transmit plant diseases. Consider using phy of managing pests using multiple control tech- control measures when insects threaten the garden. niques. IPM balances the goals of economic produc- tion and environmental stewardship when imple- Identify the insects in your garden to determine menting control practices. IPM is the overriding if they are beneficial, incidental, or pests. Learn to strategy for most of production agriculture today recognize the common insects in your area, espe- and is rapidly being adopted in home gardening as cially the pests, and learn to recognize the type of well. damage associated with pests. Monitoring or scouting crops for the presence Insect pests can enter vegetable gardens by walk- and abundance of pests is an important part of IPM. ing or flying. Flight allows many insects to have Most IPM programs reserve the use of insecticides · great mobility and their movement in large num- for situations when the pest is present in large num- bers is possible. Also, certain pests, like aphids and bers and the cost of return on the investment in con- mites, reproduce about once a week under good trol practices can be justified. conditions and their populations can increase rapid- ly. When pests seem to appear in large numbers Many specific insect control practices can be almost overnight, they have either moved in or are implemented as part of an IPM program; generally rapidly reproducing. the use of insecticides is included as a control option. When alternate control practices are substi- As insects grow, they change in size and shape. tuted for insecticides, the IPM approach is similar to This process is called metamorphosis. Some insects organic gardening. damage plants in both the immature and adult stages. Because insects change, they may be difficult Many of the insect management practices avail- to identify and the type of damage they cause also able to home vegetable gardeners are categorized in may change. Young caterpillars may barely scrape the following sections. 3 Cultural control The conservation approach to biological control is the perpetuation or encouragement of natural Cultural controls that can reduce pest popula- enemies already present in the area. Conservation tions consist of a variety of management practices methods in home gardens include providing nectar- such as crop rotation, cultivation, weed manage- producing flowers as food for insect parasites and ment, water management, and proper fertilizer use. avoiding unnecessary pesticide applications. Use fallow periods and crop rotation to interrupt the life cycles of pests whenever possible. Always Augmentation is the release of agditional preda- destroy plant debris that can harbor pests and con- tors and parasites that add to the natural popula- trol weeds because they attract insects that may tions of biological control organisms. Releases of feed on vegetables. ladybird beetles, praying mantises, parasitic wasps, and other organisms contribute to biological con- trol. However, because many of these organisms Host plant resistance occur naturally in the environment, the additional Vegetable varieties differ in susceptibility to benefit contributed by releases may be marginal. insect pests. This response is called host plant resist- There are many commercial sources of biological ance (HPR). Resistance can be expressed as toler- control agents. ance, non-preference, or antibiosis. Tolerance is the Biological control should not be considered as an ability of the plant to continue to develop and pro- instant solution to pest problems. Generally, a duce even with insect feeding. Non-preference is sound biological control program needs to be sup- exhibited when an insect prefers to feed on or lay ported by careful study and increased knowledge. eggs on alternative varieties or host plants. Proper identification of pests, careful selection of Antibiosis is the ability of a plant to kill or slow the beneficial organisms, and increased monitoring are development of a pest, usually with chemicals that all necessary for success. Biological control solutions occur naturally in the plant. Extensive variety trials cannot be implemented for all pest situations are needed to determine the HPR of vegetables. because biological control agents are not available Most variety selection emphasizes factors like for every pest. appearance, taste and production volume, not insect resis tance. Mechanical control Recently, transgenic plants have been developed for field crops and some vegetables including toma- Mechanical control is the use of physical means toes, potatoes and corn. Transgenic plants have had to reduce the number of insects or insect damage or their genetic material altered. Dramatic results have to exclude pests from the garden. Mechanical meth- been achieved when genes for resistance to insects ods include the use of barriers, covers, high pres- are incorporated into plants. Most of the resistant sure water sprays, and hand picking of pests. transgenic vegetable varieties have genes of the bac- Barriers come in many shapes and sizes. They teria Bacillus thuringiensis and are resistant through prevent the movement of pests onto the plants. antibiosis to caterpillars or beetles. Resistant trans- Cardboard or plastic cylinders around the base of genic vegetable varieties are expected to become transplants are an example of a barrier that discour- increasingly available to home gardeners in time. ages cutworms and other soil-inhabiting pests from attacking transplants. Biological control Cloth or plastic row covers can serve as a cover Biological control is the use of one. organism to to keep out pests in a newly planted garden. control another. Three approaches to biological con- Screening may increase the temperature of a plant- trol have been successfully implemented: importa- ing bed, so additional benefits of temperature man- tion, conservation and augmentation. agement may be achieved. Screening is useful for young plants and seedlings that are the most sus- Importation is the introduction of a parasite or ceptible to pest attack. predator from another country into our country to control a pest species. Importation is highly regu- High pressure water sprays are also a mechanical lated and is beyond the scope of home vegetable control method. Sprays are most effective against gardeners. We do benefit, however, from successful small, soft-bodied pests like aphids. High pressure importation programs completed by various water sprays may help remove webbing, dissolve research groups. droppings, and quickly reduce the number of pests. 4 This is one of the few options available for use Service. Results from efficacy trials were not consid- when vegetables are near harvest because of safety ered in preparation of this guide. Control results res trictions. may vary depending on the environmental condi- tions, method of application, and other factors. Hand picking and destruction of some pests may be feasible in small gardens. If persistently done, Table 2 lists product label names of insecticides hand picking can be successful in controlling toma- available for use in home gardens. It is not an to hornworms and squash bugs. Obviously, hand exhaustive list but includes most of the common picking is more feasible for larger insects than for active ingredients currently available. Use this list small insects. as a guide when purchasing products for use in home vegetable gardens. Chemical control There are numerous trade names for some gener- Pesticides come in many forms and provide a ic insecticides and special restrictions may be pres- wide array of pest management options.