Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/1997
Publication Date: N/A
Citation: Interpretive Summary: The neem tree is native to Asia and several chemicals found within the foliage and seeds of the tree have insecticidal properties. One of these chemicals, azadiractin, has been shown in laboratory tests to enhance the gypsy moth nuclear polyhedrosis virus. This enhancement would be very beneficial in the use of the virus for managing moth populations in the field because it could decrease the concentration (and cost) of virus needed to obtain adequate control. We compare the efficacy of a virus treatment on two typical host species in the mid-Atlantic region (sweetgum and white oak) in the field to establish that there was no host influence. We then treated sweetgum foliage with virus and azadirachtin combinations to examine possible enhancement of viral activity in the field. No enhancement of activity was observed. However, both the azadirachtin and the virus had significant and negative impacts on the gypsy moth larvae. While more research on the potential impact of azadirachtin on non-target insects is necessary, this compound does show some potential for use as a management tool against the gypsy moth. The results are important to other scientists and gypsy moth management personnel because compounds from neem are currently being investigated against a wide variety of insect pests including the gypsy moth.
Technical Abstract: Two field experiments were conducted to examine the efficacy of the gypsy moth nucear polyhedrosis virus (Gypchek) when consumed on sweetgum. In the first experiment, no significant differences in survival were observed for second instar larvae that consumed the virus on sweetgum or white oak foliage following an aerial application. In the second experiment, a ground application of the virus with and without azadirachtin, an insecticidal extract from the neem tree, was tested to examine the potential enhancement of viral activity by this compound. When applied to sweetgum foliage, the virus without azadirachtin treatment resulted in the highest level of mortality to second instar larvae that consumed the treatments on sweetgum foliage followed by the virus with azadirachtin treatment, the azadirachtin treatment and the controls. Therefore, there was no enhancement of viral activity when the azadirachtin was added to the formulation. The two treatments that contained azadirachtin resulted in a significant reduction in larval weight gain, probably due to a reduction in feeding by the insects after ingestion of the compound. These results suggest that ground application of either material may be useful in managing gypsy moth populations on individual trees.