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Biological Control in Pest Management Systems of Plants
Department of Entomology
Outputs: The results of the proposed research activities will consist of:
- new or improved natural enemy species or biotypes for biological control of major arthropod and weed pests in the U.S.;
- improved methods for incorporating biological control into IPM programs for key agricultural resources in the U.S. data addressing the ecological basis of success and failure of biological control; and
- data addressing the environmental and economic impacts of biological control.
The publications, presentations and website will continue to provide the state and federal agencies, and grower industry clientele with both technical and practical information on a timely basis.
Outcomes or projected Impacts: The availability of new or improved biological control options for major pest species in the U.S. will result in
- reduced pesticide usage,
- increased sustainability of agricultural production systems, and
- economic benefits to both agricultural producers (in the form of reduced pest management costs) and consumers (in the form of reduced food costs).
The attendant benefits of reducing pesticide usage include reduced food, soil and water contamination, reduced impacts on nontarget species including wildlife, and reduced human exposure to potentially harmful chemicals. Enhanced knowledge of the ecological mechanisms underlying biological control will increase success rates. Enhanced knowledge of the environmental and economic impacts of biological control will improve the environmental safety of biological control and foster its adoption in current and new pest management programs.
2011 Project Description
Research is currently ongoing throughout North America to examine the structure and function of terrestrial food webs in relation to biological control by generalist predators. Most notably, building on previous research in Kenya, collaborative research in Hawaii seeks to identify natural enemies of the coffee berry borer, a pest of increasing significance in the state. This research utilizes molecular markers developed previously to screen natural enemies from coffee plantations for the DNA of this major pest.
Research in winter wheat also seeks to address a major objective of this multi-state project, namely objective 9: implement and evaluate habitat modification, horticultural practices, and pest suppression tactics to conserve natural enemy activity. This research in winter wheat is exploring ways that natural weed strips provide a conservation boundary to real-production wheat that can serve to mitigate the effects of virus transmission by aphids. The central premise to this work is that the provisioning of refugia surrounding crop fields enhances natural enemy populations that directly impact pest densities and thus reduce disease transmission. The integration of immunoassay, molecular and ecological experiments that utilize spatial models are being analyzed to examine the source/sink dynamics of predator and prey populations within these refugia.
Other aspects of research clearly address Objective 7: Characterize and identify pest and natural enemy communities and their interactions. Through the development and application of molecular tools, research continues to explore open-field interactions in a variety of cropping systems (wheat, corn, soybean, alfalfa, potato, coffee) that reliably documents the role of predators in pest suppression.
Twenty three research presentations were given at regional, national and international meetings by the PI, graduate students and postdoctoral scholars. Meetings where research was presented were as follows: Entomological Society of America Annual Meeting (Reno, NV), International Meeting on Understanding and Managing Ecological Novelty (Monte Verita, Switzerland), American Arachnological Society Annual Meeting (Portland, OR), Entomological Society of America North Central Branch Annual Meeting (Minneapolis, MN) and the Entomological Society of America Pacific Branch Meeting (Kona, HI). These included four invited symposium presentations.
(1) Use of generalist predators for management of invasive pests in strawberry agroecosystems. Diagnostic molecular gut-content analysis was used to examine the strength of trophic interactions between carabid beetles and slugs. Field collections revealed two major predators of slugs, Harpalus pennsylvanicus and Chlaenius tricolor, which revealed the potential importance of these natural enemies of slugs in the Nearctic. Additionally, detrital subsidies were adopted to examine whether the addition of structural complexity in the agroecosystem provided enhanced biological control benefits. Although results were inconclusive (adverse weather conditions prevented rigorous statistical analysis), the possibility exists that the provisioning of detrital supplementation and habitat complexity could enhance natural biological control in strawberry agroecosystems.
(2) Phenological dynamics of predators in alfalfa. Agroecosystems are characterized by high disturbance that required rapid recolonization of the habitat for natural enemies to successfully impact pest populations. Web-building spiders form a major component of this natural enemy fauna and have been purported to contribute to the biological control of a variety of pests such as aphids and leafhoppers. However, their success is reliant on their ability to adapt to these highly disturbed environments. Large scale field research was integrated with time-series analysis to reveal phonological patterns of immigration by predators in relation to crop cycles in alfalfa. Crucially, the timing of peak immigration corresponded with the early phase of the pest population cycle, during which natural enemies have the maximum impact on pest populations. This suggests that these predators are capable of contributing to pest suppression as part of the assemblage of natural enemies and has the capacity to be integrated into future pest management decisions.
(3) Importance of non-pest prey for aphidophagous coccinellids. Non-prey food items have the capacity to sustain generalist natural enemies when pest populations are low. Thus they serve as a critical resource in biological control programs and their diversity can enhance the fitness and fecundity of predators. Using a Diptera-specific monoclonal antibody, research examined the importance of these non-pest prey to coccinellid larvae, themselves major predators of pest aphids. Significant numbers of predators screened positive for dipteran prey, suggesting that they provide a valuable (and previously undocumented) food resource in the field.
(4) Interaction of transgenic crops with spiders. Genetically engineered crops are an important part of the agricultural landscape. Therefore understanding the interaction between these crops, natural enemies and prey biodiversity is crucially important. In a major meta-analysis, spider families responded differently to Bt crops, and spider responses to insecticides are species- and toxin-specific, thus highlighting the need for greater taxonomic resolution in future research.
Eskelson, M.J., Chapman, E.G., Archbold, D.D., Obrycki, J.J., Harwood, J.D. (2011). Molecular identification of predation by carabid beetles on exotic and native slugs in a strawberry agroecosystem. Biological Control, 56, 245-253.
Moser, S.E., Kajita, Y., Harwood, J.D., Obrycki, J.J. (2011). Evidence for utilization of Diptera in the diet of field-collected coccinellid larvae from an antibody-based detection system. Biological Control, 58, 248-254.
Peterson, J.A., Lundgren, J.G., Harwood, J.D. (2011). Interactions of transgenic Bacillus thuringiensis crops with spiders (Araneae). Journal of Arachnology, 39, 1-21.
Welch, K.D., Crain, P.R., Harwood, J.D. (2011). Successional dynamics of web-building spiders in alfalfa: implications for biological control. Journal of Arachnology, 39, 244-249.