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Title: INTEGRATING ARTHROPOD HERBIVORY AND REDUCED HERBICIDE USE FOR WEED MANAGEMENT

Author
item Williams, Martin
item WALSH, DOUGLAS - WASHINGTON STATE UNIV
item Boydston, Rick

Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2004
Publication Date: 12/1/2004
Citation: Williams, M.M., Walsh, D.B., Boydston, R.A. 2004. Integrating arthropod herbivory and reduced herbicide use for weed management. Weed Science. 52:1018-1025.

Interpretive Summary: ntegrated weed management (IWM) aims to reduce weed fitness through a series of mortality and fitness-reducing events. However, few have examined how arthropod herbivory, as biological control, and herbicides can be combined. We developed a model study system that quantified the response of volunteer potato to fluroxypyr dose and Colorado potato beetle herbivory. Over a range of fluroxypyr doses, volunteer potato fitness often was reduced with herbivory, compared to no herbivory. The impact of the research is that it provides new methodology for studying the interaction between IWM components and new opportunities for reducing herbicide use while maintaining weed suppression.

Technical Abstract: Few studies have examined the combined effect of herbicide-induced stress and arthropod herbivory on weed fitness. The purpose of this work was to quantify the effect of Colorado potato beetle (CPB) herbivory on the fluroxypyr dose response of volunteer potato. Herbicide dose response bioassays were conducted in the presence and absence of CPB herbivory. Logistic model parameter estimates and a fixed response dose (FRD) for leaf area, shoot biomass, tuber number, and tuber biomass were often lower with herbivory, compared to no herbivory. Results from short-season field studies (1,000 GDD following postemergence (POST) herbicide application) indicated herbivory had the most effect on potato during a period that coincided with high CPB density and optimal temperatures for CPB development. Season-long bioassays (>3,100 GDD following POST) revealed herbivory reduced FRD 65 and >85% for tuber number and tuber biomass, respectively. Integrated weed management systems targeting volunteer potato could be more effective when fluroxypyr applications are made during periods of high herbivory.