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Agronomy Day 2008

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Tour B

Changing Tactics: The Battle Against Soybean Aphids Using Insecticides and Host Plant Resistance

Ronald E. Estes
Ronald E. Estes
Senior Research Specialist
Department of Crop Sciences
Nicholas A. Tinsley
Nicholas A. Tinsley
Graduate Research Assistant
Department of Crop Sciences

Since 2001, the soybean aphid, Aphis glycines, has threatened soybean production somewhere in the Midwest almost every year. In 2003, millions of soybean acres were sprayed with insecticides for control of soybean aphids, and yield losses in non-treated fields were substantial. The management tool of choice to control soybean aphids has been foliar applied insecticides. More recently, a trend towards using tank mixes or products containing a combination of both an organophosphate for quick knockdown and a pyrethroid for longer residual activity has become more common. Additionally, seed applied insecticides show some value in slowing aphid population increases, providing growers with additional time to make foliar applications.

An exciting new option in the battle against soybean aphids comes in the form of host plant resistance. Researchers at major land grant universities, including the University of Illinois have been developing soybean lines with resistance to the aphid in the past few years. Results from University of Illinois efficacy trials indicate that resistant soybean lines show good potential for future soybean aphid management. The idea that soybean aphids may be suppressed without insecticide applications is attractive. However, there are many unanswered questions regarding soybean aphid host plant resistance. Can consistently effective levels of resistance be incorporated into high-yielding soybean varieties? Does resistance suppress soybean aphids throughout the season? How does resistance affect natural enemies of the soybean aphid? These questions have been central to soybean aphid research projects across the Midwest.

The soybean aphid situation for this growing season will be reviewed, followed by a discussion of insights gained from our research in 2007. We will also offer updates on the status of our 2008 soybean aphid research program. Topics for discussion include efficacy of seed applied insecticides, foliar applied insecticides, and resistant varieties. We also will offer comments on the unique challenges posed by soybean aphid host plant resistance.

soybean aphids natural enemies of the soybean aphid
Illinois Soybean Association
Photos courtesy of David Voegtlin
Energizing Agriculture