Botanical insecticides are naturally occurring chemicals extracted from plants. Natural pesticidal products are available as an alternative to synthetic chemical formulations but they are not necessarily less toxic to humans. Some of the most deadly, fast acting toxins and potent carcinogens occur naturally. Some of the botanical pesticides are very toxic to fish and other cold-blooded creatures and should be treated with care. Protective clothing should be worn when spraying, even though their toxicity is normally low to warm-blooded animals. Botanical insecticides break down readily in soil and are not stored in plant or animal tissue. Often their effects are not as long lasting as those of synthetic pesticides and some of these products may be very difficult to find.

Citrus oil (limonene, linalool) are extracts from citrus peels primarily used as flea dips, but have been combined with soaps as contact poisons against aphids and mites. They evaporate quickly after application and provide no residual control.

Nicotine concentrate is very poisonous if inhaled. It is derived from tobacco and is commonly sold as a 40 percent nicotine sulfate concentrate. Nicotine is a fast acting contact killer for soft bodied insects, but does not kill most chewing insects. It is less effective when applied during cool weather. Do not spray within 7 days of harvest.

Pyrethrin is a fast acting contact poison derived from the pyrethrum daisy. It is very toxic to cold blooded animals. Some people and most cats have allergic reactions to it. Pyrethrin is effective on most insects, but does not control mites. It rapidly breaks down in sunlight, air and water.

Rotenone is derived from the roots of over 68 plant species, and is very toxic to fish, pigs, and cool-blooded animals. It has a short residual. Rotenone is a broad spectrum poison mainly used to control leaf-eating caterpillars and beetles. Direct contact may cause skin and mucous membrane irritation. It is more toxic when inhaled.

Ryania is a slow acting stomach poison. It has a longer residual than most botanicals. Toxicity to mammals is moderate.

Sabadilla is derived from the seeds of South American lilies. It is a broad spectrum contact poison, but has some activity as a stomach poison. It is most effective against true bugs such as harlequin bugs and squash bugs. Sabadilla degrades rapidly in air and sunlight, and has little residual toxicity. It is very toxic to honey bees. The least toxic botanical to humans.

Neem is a relatively new product on the market. It is derived from the neem tree that grows in arid tropical regions. Extracts from the neem tree have been reported to control over 200 types of insects, mites, and nematodes. The neem spray solution should not be exposed to sunlight and must be prepared with water having a temperature between 50 and 90°F. The solution is effective for only 8 hours after mixing. Neem is most effective under humid conditions or when the insect and plants are damp. It has a low toxicity to mammals.

Insecticide Use Against
Pyrethrum Pickleworms, aphids, leafhoppers, spider mites, harlequin bugs, cabbage worms.
Neem Cutworms, armyworms, sodworms.
Rotenone Spittlebugs, aphids, potato beetles, harlequin bugs, chinch bugs, spider mites, carpenter ants.
Ryania Codling moths, Japanese beetles, squash bugs, potato aphids, onion thrips, corn earworms, silkworms.
Sabadilla Grasshoppers, codling moths, moths, armyworms, aphids, cabbage loopers, blister beetles, squash bugs, harlequin bugs.
Nicotine Aphids, thrips, caterpillars.

Consumer Horticulture | Quick Reference

© Erv Evans, Consumer Horticulturist
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