neem oil Neem oil is a natural way to control aphids, whiteflies, flea beetles and other small insects. It's pressed from the seeds of the Neem tree, a fast-growing tree in tropical and subtropical regions. The active compound is Azadirachtin, a compound that interferes with an insect's hormones and makes it hard from them to reproduce or eat. It degrades quickly and will not harm beneficial insects. If you're looking for instant gratification, you're not going to get it with neem oil. It does not kill insects on contact, but be sure that in a couple days insects will feel the effects. For best results, mix neem with warm water and a surfactant (dish soap). Thoroughly spray the leaves with a fine mist, taking care to cover both the top and bottom of each leaf. Because it's an oil, do not apply in hot sun or you may burn the plant. Repeat as directed by the label, and read the label to see what plants are sensitive to neem.