Neem Oil Is Probably Best Known For Its Use As A Safe And Effective Insecticide. Neem Oil Is A Natural Byproduct Of The Neem Tree, This Makes It Organic And Biodegradable. Since Neem Oil Can Kill Insects At Varying Insects, You Can Use It As A Dormant-season Application To Kill Overwinter Pests And Eggs Or As A Foliar Spray To Repel And Kill Insects. Neem Oil Is An Effective Pesticide That Gets Rid Of Over 600 Species Of Insects, Not Just A Few, Including Insects, Fungi, Nematodes And Viruses.