Crop rotation, good soil and plant health, and biological controls such as beneficial insects, including lady bugs and various wasps, are the favored organic methods for controlling pests, notes the University of Connecticut Integrated Pest Management website. If an invasion of caterpillars or leaf miners threatens to defoliate your tomatoes almost overnight, however, you may want to turn to organic pesticides that rely on natural extracts rather than synthetic chemicals to kill pests. The OMRI (Organic Materials Review Institute) seal on the product container signifies it is safe to use in organic production.
Bacillus thuringiensis kurstaki, or bT (sold as Dipel, Javelin, Thuricide, MVP and under other names), is a treatment of choice for caterpillars, including tomato hornworms, fruitworms and pinworms, as well as fungus gnat larvae. This naturally occurring pathogen makes the caterpillars sick when they eat it. Other microbial pesticides formulated from microorganisms or their byproducts include spinosad, a bacterium that attacks the nervous systems of caterpillars, leaf miners and thrips. These are safer to use than botanicals and more selective in what they kill. Cover tomatoes thoroughly with the spray or dust so the pests ingest the microbial agent.
Rotenone, pyrethrum, sabadilla and other botanicals are derived from plants. Pyrethrum, for example, is extracted from chrysanthemums, and rotenone from the roots of a member of the bean family, notes Margaret Geick of the Colorado State University Cooperative Extension. Extracts from neem tree seeds, sold as Azatin and Align, inhibit development of young insects and deter feeding by adults. Botanicals break down rapidly in the presence of light and air, states the University of Connecticut, and provide pest control for only a day or two. They may kill beneficial insects, too. Apply botanicals directly to your plants with a trigger sprayer or hand duster.
Soaps work by smothering thrips, aphids and other soft-bodied insects. Horticultural oils are based on petroleum products and allowed as a means of smothering insects as well. Apply synthetics directly to tomato plants with a trigger sprayer or pump sprayer.
Sulphur and copper are used to prevent disease caused by bacteria and fungus. Formulations include Bordeaux mixture, copper hydroxide (Kocide), copper sulfate, tri-basic copper and copper-zinc mixtures. Spray these mineral products on the plant with a pump sprayer. Diatomaceous earth may be classified as a mineral or a biological. These one-celled diatoms, applied by a hand duster to the tomato plant, dry out soft-bodied insects.