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United States Department of Agriculture

Agricultural Research Service

Title: Improvement of the Residual Activity of a Cucurbitacin-Based Adult Corn Rootworm Insecticide

Authors
item Pingel, Randall
item BEHLE, ROBERT
item MCGUIRE, MICHAEL
item Shasha, B - RETIRED, USDA-ARS-NCAUR

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 5, 2001
Publication Date: October 15, 2001
Citation: J. ENTOMOL. SCI. 2001. VOL. 36(4):416-425.

Interpretive Summary: Areawide management of corn rootworms focuses on managing adult beetles to decrease the number of females laying eggs and thus decrease the number of larvae in the corn fields of the next growing season. The primary tool used to manage the beetles is an environmentally friendly, insecticidal bait. The success of the program to manage the beetles, and ultimately the adoption by growers of the program's practices, is largely dependent on ability of the bait to resist wash-off by rain. The objective of this research was to increase the length of time the bait remains active after application by adding adjuvants to the spray tank or as a part of the formulation to prevent wash-off by rain. Results of small plot experiments suggested that there was a trend for less residual activity with higher concentrations of adjuvant and demonstrated that low pH gluten was more effective than lignin for resisting wash-off by natural rain when added to the bait as a formulation ingredient. Large-plot experiments conducted over two years in growers's fields failed to show a significant advantage of gluten and lignin adjuvants when compared with the bait without adjuvants. For both years, all bait treatments provided adequate management of the adult corn rootworm for 3 weeks after application. In addition, the number of beneficial insects were not reduced after bait applications. Our research shows that the additives did not detract from the efficacy of the bait formulations and suggests the residual activity of insecticidal bait may be improved by using appropriate adjuvants or by improved formulations. The manufacturer of the bait has added gluten to their bait formulation.

Technical Abstract: Areawide management of the corn rootworm, Diabrotica spp., focuses on managing adult beetles to decrease egg deposition and thus decrease the number of future larvae. The primary management tool for this program is commercial bait composed of a feeding stimulant (cucurbitacin), inert ingredients, and a small quantity of insecticide. The objective of this research was to improve the residual activity of the bait by preventing wash-off by rainfall; various lignin and gluten materials were tested as tank mixed adjuvants or as a part of the formulation for two commercial bait formulations, Slam Prader and Slam SD. Small-plot experiments identified low pH gluten and sodium lignate to have the greatest potential to provide rainfastness and demonstrated that low pH gluten was more effective than lignin for resisting wash-off by natural rain when added to the bait as a formulation ingredient. Results also suggested that there was a trend for less residual activity with higher concentrations (>2% of spray volume) of adjuvant. Large-plot experiments conducted over two years in grower's fields failed to show a significant advantage of gluten and lignin adjuvants compared with the bait without adjuvants; however, all bait treatments provided adequate management of the adult corn rootworm for three weeks after application. Also, counts of ladybeetles and lacewings indicated only minimal impact of insecticidal treatments on beneficial insects. Our research suggests the residual activity of insecticidal bait may be improved by using appropriate adjuvants or by improved formulations.

Last Modified: 7/28/2014
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