NEEM OIL AND NEEM OIL COMPONENTS AFFECT THE EFFICACY OF COMMERCIAL NEEM INSECTICIDES

A series of toxicity studies with pea aphid, Acyrthosiphon pisum (Harr is) and the neem insecticides Margosan-O (MO), MO devoid of neem oil, Azatin, RH-9999, Azatin with 5% neem oil, RH-9999 with 5% neem oil, an d neem oil (5%) were conducted. We found that addition of neem oil inc reased the efficacy of neem insecticides that did not contain the oil, while removal of neem oil from MO reduced its efficacy 62%. Neem oil was also extracted with methanol. When methanol-extracted neem oil was added to MO devoid of neem oil, its efficacy was still 30% lower than MO. Addition of canola oil gave a similar response. Six limonoids, ni mbandiol, deacetylnimbin, 6-acetylnimbandiol, deacetylsalannin, nimbin , and salannin, and two unidentified chemicals, believed to be limonoi ds, were identified in neem oil. Our data indicate that neem oil and o ther oils increase the efficacy of neem insecticides, but a polar comp onent(s) of neem oil also contributes to increased biological activity of neem insecticides.