Answer: I know the tobacco companies probably wouldn't want me to say this, but the active ingredient from the tobacco spray that poisoneds pests is nicotine, which is a very lethal, broad-spectrum poison, meaning that it'll kill most everything in its path. It's no longer recommended as a home garden remedy. There are other "botanical" insecticides available on the market that are much safer when used as directed: pyrethrum and neem are two such insecticides which are quite popular these days. They are also broad-spectrum, but when you use them properly and only when truly needed, you can have less impact on non-target and beneficial species. Just recently, cottonseed oil has been formulated for use as a suffocating oil spray for use against scale, mealybugs, and other pests.
Other organic sprays are biological controls, such as Bt (Bacillus thuringiensis), a bacterium that infects only insects. Different strains of the bacterium attack caterpillars, Colorado potato beetle larvae, and mosquito larvae.
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