Natural Controls

Biological Insecticides
The advantage of using either biological or microbial insecticides is that they are only harmful to specifically targeted pests. They are not injurious to wildlife, humans, or other soil microbes or insects. Furthermore, they don't leave toxic residues behind to worry about. They do come with an admonition, though. The mold spores, bacterial spores, and other living organisms that make up these products can produce allergic reactions in some people. Handle them with care, wear protective clothing, avoid inhaling them or rubbing them on your skin, and follow all provided directions.

Bacillus thuringiensis: (BT) is composed of a crystalline protein produced by the spores of a soil bacterium. When ingested by target pests, it destroys the gut lining, stopping their feeding and killing them. Insect-specific strains are sold as dusts, emulsions, and wettable powder. BT is highly selective and viable for only a few days after application. Apply in late afternoon for the best results.

Bacillus popilliae: or milky spore disease, has been the chief biological agent for Japanese beetle control. Its efficacy is now in question, however, especially in northern soils. Check with your Cooperative Extension Service for local recommendations. Only one or two applications of milky spore disease are needed because, once it kills the grubs, fungal endospores are released into the soil to await their next host. However, this product is not effective for other kinds of white grubs.

Steinernema glaseri and Steinernema carpocapsae: Predatory nematodes useful for attacking lawn pests such as billbugs, sod webworms, and white grubs. These microscopic, wormlike creatures live in moist soil and attack the larvae of certain pests. Beneficial nematodes are not harmful to plants, and different strains are sold to target specific pests. The use of predatory nematodes is a quickly growing area of horticultural research that shows much promise. See the section "Nematodes" for more information.

Botanical Insecticides
Botanical insecticides are not targeted to specific pests, and they often kill beneficial insects as well. They are best used only as a last resort, when more directed methods fail. Although they do not persist long in the environment, botanical insecticides can be quite toxic when applied, so handle them with extreme care and always follow package directions, including wearing protective clothing.

Pyrethrins: These insecticides are made from extracts of pyrethrum flowers, two species of chrysanthemum. Known for their ability to "knock-down" flying insects, pyrethrins are frequently combined with synergists, such as pipernyl butoxide, which increases the pyrethins' toxicity and length of residual action. Used against aphids, armyworms, beetles, caterpillars, leafhoppers, and other pests, pyrethrins are also toxic to fish and some beneficial insects.

Rotenone: One of the oldest botanical insecticides, Rotenone is extracted from the roots of Asian derris plants. Caution: This slow-acting general insecticide is highly toxic to fish and moderately so for mammals. It is also very irritating to the respiratory tract. Keep children and pets away, and be sure to follow application guidelines.

Sabadilla: One of the least toxic botanical insecticides, Sabadilla is made from the seeds of the Venezualan plant sabadilla (Schoenocaulon officinale). Used as a dust or spray to kill grasshoppers, armyworms, webworms, aphids, and chinch bugs, this insecticide breaks down rapidly in sunlight. Sabadilla is highly irritating to the respiratory tract and eyes.

Neem : This product is derived from an oil extracted from the Indian neem tree. It is effective on multiple fronts--repelling insects, stopping them from feeding, inhibiting molting, and suppressing growth. Neem affects leaf-chewing beetles, caterpillars, and other insects going through metamorphosis. It has low toxicity for mammals.

Mycoinsecticides
The Beauveria bassiana fungus was discovered in 1835, but it was not until recently that its potential as an insecticide was realized. Now this common soil-borne fungus has found a use in Integrated Pest Management (IPM) programs because of its low toxicity and ability to kill insect pest without harming most beneficials. Results vary, but generally this fungus offers good control of sod webworms, fall armyworms, billbugs, chinch bugs, aphids, and white grubs, among others.

A thorough spraying of targeted pests is necessary because successful infection is dependent on direct contact with the fungus. Under favorable conditions, the fungal spores penetrate the insect's body, where they secrete a killing toxin. Death of the host usually takes three to seven days. Beauveria bassiana is now being produced commercially and has been registered with the EPA for use in landscapes.

Insecticidal Soaps
Insecticidal soaps are made from the potassium salts of fatty acids. On direct contact with susceptible insects, these acids disrupt the structure and permeability of their cell membranes, causing desiccation and death. Most effective on soft-bodied insects, including beneficials, these soaps have a minimal impact on ladybug larvae and parasitic wasps. Aside from causing mild eye and skin irritation, they have low mammalian toxicity. They are biodegradable. However, once they dry, they are no longer effective.