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United States Department of Agriculture

Agricultural Research Service

Research Project: EPIDEMIOLOGY AND MANAGEMENT OF XYLELLA FASTIDIOSA (XF) AND OTHER EXOTIC AND INVASIVE DISEASES AND INSECT PESTS

Location: Crop Diseases, Pests and Genetics

Title: Synergistic interactions between entomopathogenic nematodes and Bt crops: integrating biological control and resistance management

Authors
item Gassmann, Aaron - UNIVERSITY OF ARIZONA
item Stock, Patricia - UNIVERSITY OF ARIZONA
item Sisterson, Mark
item Carriere, Yves - UNIVERSITY OF ARIZONA
item Tabashnik, Bruce - UNIVERSITY OF ARIZONA

Submitted to: Journal of Applied Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 2007
Publication Date: May 13, 2008
Citation: Gassmann, A.J., Stock, P.S., Sisterson, M.S., Carriere, Y., Tabashnik, B.E. 2008. Synergistic interactions between entomopathogenic nematodes and Bt crops: integrating biological control and resistance management. Journal of Applied Ecology 45:957-966.

Interpretive Summary: Crops genetically modified to produce Bacillus thuringiensis (Bt) toxins are widely planted. Management of target pests in Bt cropping systems is complicated because pest populations must be managed to minimize economic damage while minimizing the risk of resistance evolution. Management options in non-Bt fields (i.e., refuges) which induce fitness costs to resistance would aid in achieving this goal. We tested whether entomopathogenic nematodes might act synergistically with Bt crops by increasing fitness costs of resistance to Bt toxins. We also tested whether insect mortality and fitness costs were affected by the cotton phytochemical gossypol. The entomopathogenic nematode Steinernema riobrave increased the fitness cost of Bt resistance, indicating that its presence in refuges may slow pest adaptation to Bt crops. No effect on fitness costs was detected for the nematode Heterorhabditis bacteriophora. Gossypol did not alter nematode-imposed fitness costs. Simulation modeling supported the hypothesis that the presence of nematodes in non-Bt refuges may slow resistance evolution. Results from this study will aid in the development of novel refuge management strategies which will minimize pest population sizes in refuges and delay resistance evolution.

Technical Abstract: Increased use of crops genetically modified to produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) presents the challenge of designing agricultural systems to manage pests and the evolution of resistance to Bt. We tested whether entomopathogenic nematodes might act synergistically with Bt crops by killing pests in non-Bt refuges and by increasing fitness costs of resistance to Bt. We also tested whether insect mortality and fitness costs were affected by the cotton phytochemical gossypol. The entomopathogenic nematode Steinernema riobrave increased the fitness cost of Bt resistance, indicating that its presence in refuges may slow pest adaptation to Bt crops. No effect on fitness costs was detected for the nematode Heterorhabditis bacteriophora. Gossypol did not alter nematode-imposed fitness costs. Simulation modeling supported the hypothesis that the presence of nematodes in non-Bt refuges may slow resistance evolution. Effects of gossypol on insect mortality from nematodes and nematode reproduction differed between nematode species. Gossypol increased insect mortality caused by H. bacteriophora but did not affect mortality caused by S. riobrave. Gossypol enhanced reproduction of H. bacteriophora and decreased reproduction of S. riobrave. Entomopathogenic nematodes have the potential to act synergistically with Bt crops because they might delay the evolution of resistance to Bt and suppress pest populations in non-Bt refuges.

Last Modified: 7/28/2014
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