Biopesticides for Control of Douglas-fir Tussock Moth

Research Issue

TM Biocontrol-1 is a viral biopesticide produced by the U.S. Forest Service that is used, along with various commercial Bacillus thuringiensis (Bt) products, for the control of the Douglas-fir tussock moth (DFTM), Orgyia pseudotsugata, in the Pacific Northwest. Improving the efficacy of these products involves bioassay in a standard (Goose Lake) strain of tussock moth that is reared to maintain vigor and provide an on-demand larval resource for research and evaluation of a variety of biological products.

 Our Research

We are researching two closely connected aspects of the DFTM: (1) improving current rearing technology to reduce costs while maintaining strain vigor and (2) refining selection and application protocols for microbial pesticides through laboratory assays in the Goose Lake strain of DFTM.

Expected Outcomes

We expect to: (1) develop an improved, cost-effective rearing protocol for DFTM including an artificial diet for rearing to the adult stage; (2) Improve protocols for the selection of Bt products for DFTM control; and (3) determine of nucleopolyhedrovirus potency in TM Biocontrol-1 stocks to establish dosages for aerial and ground-based application programs.

Research Results

A critical step in determining pathogenicity of Bt products for DFTM  is the binding insecticidal proteins Cry toxins to specific cell receptors in the insect gut. Fluorescence microscopy has shown the presence of two Bt toxin receptors, BTR-270 and APN (for Cry1Aa and Cry1Ac toxin binding) in tissue sections of early fourth instar DFTM larvae. This experimental approach can be valuable for preliminary screening of Bt Cry proteins to discriminate between potentially lethal and nontoxic Bt Cry proteins. Although specific toxin binding of Cry proteins to midgut brush border membranes in target insect pests is indicative of toxicity, results will be confirmed with further testing.

Valaitis, A.P.; Podgwaite, J.D. In press. Comparative analysis of Bacillus thuringiensis toxin binding to gypsy moth, browntail moth and Douglas-fir tussock moth midgut tissue sections using fluorescence microscopy. In: McManus, K. and Gottschalk, K., eds. Proceedings, 20th USDA Iinteragency Research Forum on Gypsy Moth and Other Invasive Species, 2010.

Research Participants

Principal Investigator

• John D. Podgwaite, Research Microbiologist, U.S. Forest Service, Northern Research Station

Research Partners

• Al Valaitis, Research Biologist, U.S. Forest Service, Northern Research Station
• Iral Ragenovic, Entomologist, U.S. Forest Service, Forest Health Protection, Pacific Northwest Research Station
• Imre Otvos, Natural Resources Canada, Canadian Forest Service, Entomologist
• Richard Reardon, Entomologist, U.S. Forest Service, Forest Health Technology Enterprise Team