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ARS Home » Research » Publications at this Location » Publication #94558
Title: AERIAL APPLICATION OF REDUCED DOSES OF GYPSY MOTH (LEPIDOPTERA: LYMANTRIIDAE) NUCLEAR POLYHEDROSIS VIRUS AND THE VIRAL ENHANCER, BLANKOPHOR BBH

Author
item Thorpe, Kevin
item COOK, STEPHEN - UNIV. OKLAHOMA
item Webb, Ralph
item PODGWAITE, JOHN - USDA, FOREST SERVICE
item REARDON, RICHARD - USDA, FOREST SERVICE

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The gypsy moth is serious pests of hardwood trees in the northeastern United States, and more than five million acres have been sprayed with chemical or microbial insecticides over the past decade to protect trees from this pest. The most environmentally benign insecticide available is Gypchek, a virus that infects only the gypsy moth. Unfortunately, this product is not commercially available, primarily because it is costly to produce. In ground-based sprays the addition of the enhancer, Blankophor BBH, to the virus made it possible to reduce the virus dose without losing effectiveness. This study was conducted to determine if lower doses can be used in aerial application if the enhancer is used. The addition of the enhancer at concentrations that were effective in the ground- based tests did not provide effective control in aerial tests. Analysis of spray deposits showed that not enough enhancer was reaching the leaf surface to be effective. Based on separate laboratory tests, it was determined that the enhancer would need to be applied at a much higher concentration or a different, more effective enhancer would be needed for aerial applications. These findings are important because they identify the additional research and development that is needed to reduce the costs of using Gypchek, possibly leading to a commercially available product which can be used by gypsy moth managers, arborists, and government agencies for gypsy moth control in environmentally sensitive situations.

Technical Abstract: The viral enhancer, Blankophor BBH, was applied by air to gypsy moth, Lymantria dispar L., populations in two formulations of gypsy moth nuclear polyhedrosis virus to determine if the enhancer could compensate for reduced doses of virus. Larval mortality in plots treated with a molasses-based formulation at one-tenth the USDA, Forest Service-recommended dose was 25% greater than in untreated plots. There was no increase in larval mortality in plots treated with an experimental wettable-powder formulation at one-fifth the recommended virus dose. The addition of 0.5% (W:V) Blankophor BBH did not increase the efficacy of either formulation. The volume of spray deposited on leaf surfaces averaged 16.6 and 40.0 nl/cm2 for the molasses-based formulation and 6.9 and 13.7 nl/cm2 for the wettable-powder formulation with and without enhancer, respectively. A separate laboratory experiment demonstrated that a dose of 1.5 ug of Blankophor BBH is required to cause >90% larval mortality among larvae exposed to a low dose of virus. Based on the spray deposit values given above, only 0.06 - 0.2 ug of Blankophor BBH was deposited per cm2 of leaf surface, which is substantially below the amount required for enhancement. The LD50 was 2.8 times greater when oak versus lettuce was used as a host substrate without Blankophor BBH, and 1.9 times greater with Blankophor BBH, respectively. The enhancer reduced LD50 values 213- and 314-fold on lettuce and oak, respectively.