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Title: RESEARCH TOWARD AUGMENTING NUCLEAR POLYHENDROSIS VIRUS LOAD IN GYPSY MOTH (LEPIDOPTERA: LYMANTRIIDAE) POPULATIONS BY EGG MASS TREATMENT

Author
item Webb, Ralph
item White, Geoffrey
item Thorpe, Kevin

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2002
Publication Date: 4/3/2004
Citation: Webb, R.E., White, G.B., Thorpe, K.W. 2004. Research toward augmenting nuclear polyhendrosis virus load in gypsy moth (lepidoptera: lymantriidae) populations by egg mass treatment. Journal of Entomological Science.

Interpretive Summary: The gypsy moth is a serious defoliator of forest and shade trees. This is a report of research toward augmenting LdNPV levels in gypsy moth populations with low virus incidence. Such populations include newly-infested leading edge areas and populations in generally infested areas where gypsy moth populations have collapsed and have held at very low levels for several years. The present study investigated egg mass treatment for introducing LdNPV into virus-free populations. We first conducted a laboratory study to determine the approximate LdNPV dose to apply to egg masses, with and without the addition of the virus enhancer Blankophor BBH to the spray mixture. We then conducted a field study to assess the effect of timing of application in the spring that also included an assessment of the addition of Blankophor BBH to the spray mixture. Finally, we determined the effect of time of application of LdNPV to pupae or egg masses by applying the virus to pupae massed under burlap bands just prior to female emergence from pupae in June, 1998. This was compared to results from an application of virus made to egg masses just prior to egg hatch in 1999. Results should be of interest to local, state, and federal workers charged with managing the gypsy moth.

Technical Abstract: We have developed procedures for augmenting LdNPV in LdNPV-depleted gypsy moth populations by egg mass contamination. We first conducted a laboratory study to determine the approximate LdNPV dose to apply to egg masses, with and without the addition of the virus enhancer Blankophor BBH to the spray mixture. We then conducted a field study to assess the effect of timing of application in the spring that also included an assessment of the addition of Blankophor BBH to the spray mixture. While application of LdNPV + Blankophor BBH resulted in faster kill, and perhaps a slightly higher level of kill, a higher number of cadavers than expected in the LdNPV + Blankophor BBH treatments had few or no polyhedral inclusion bodies (PIBS). Finally, we determined the effect of time of application of LdNPV to pupae or egg masses on the level of virus infection of larvae emerging from treated egg masses. An April 1999 treatment to egg masses clearly resulted in a higher kill of larvae emerging from egg masses compared with a June 1998 treatment to female pupae (with virus incorporated into the egg masses laid by females after adult emergence). The season-long recovery of virus from populations in the treated plots versus control plots provided proof- of-concept that LdNPV can be inoculated into gypsy moth populations by egg mass treatment.