Because of its short persistence, its effectiveness is limited but so are its impacts on natural insect enemies. Neem is an exciting, new insecticide product. Extracted from the seeds of the tropical neem tree, this plant substance has long been used in Africa as a pharmaceutical and toothpaste. Neem has recently been found to interfere with insect feeding and development. Treated insects rarely show immediate symptoms, and death may be delayed a week or longer.
Insects are sluggish after spraying, however, and do little feeding.
Labeled uses of neem are still under development. Its very low toxicity and increasing labeling for a wide number of insects make it an attractive, up and coming insecticide. CSU research tests show good activity against tent caterpillars and elm leaf beetles, and fair results with tussock moth. The container in which an insecticide is sold will have a label that tells the user not only what pests the product can control, but also safety precautions for the applicator and the environment. The most important thing in choosing an insecticide is not its origin but its label.