Monday, December 11, 2006 - 11:23 AM

Co-management of soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) and bean leaf beetle Cerotoma trifurcata (Förster) (Coleoptera: Chrysomelidae) in Iowa

Kevin D. Johnson,, Matthew E. O'Neal,, Jeffrey Bradshaw,, and Marlin E. Rice, Iowa State University, 113A Insectary, Ames, IA

In Iowa, soybean, Glycine max (L.), production has been complicated by the arrival of the soybean aphid Aphis glycines, Matsumura (Hemiptera: Aphididae), and economic populations of bean leaf beetle, Cerotoma trifurcata (Förster) (Coleoptera: Chrysomelidae). Insecticides applied to reduce populations of both the overwintering population and first generation of C. trifurcata were evaluated during 2004-2006 for their impacts on A. glycines populations. There was no significant overlap of either overwintering populations or the first generation of C. trifurcata with A. glycines as aphid populations did not reach economic levels until early August. During this study, insecticides targeting C. trifurcata did not prevent economic populations or consistently reduce populations of A. glycines compared to an untreated control. The highest populations of A. glycines occurred when lambda-cyhalothrin (178 ml/ha) was applied to the overwintering population of C. trifurcata. In a second study, foliar insecticides applied based on a threshold of 250 A. glycines per plant reduced aphid exposure and protected yield better than preventative insecticide seed treatments. Furthermore, foliar applied imidacloprid at a threshold of 250 per plant had a greater impact on A. glycines populations (and greater yield protection) than imidacloprid applied as a seed treatment. For the prevention of soybean yield loss from A. glycines, the use of insecticides targeting overwintered or first generation C. trifurcata failed to protect soybean yield compared to the control, and a preventative insecticide program did not provide better protection compared to a single foliar insecticide applied based on a threshold for A. glycines.

Species 1: Hemiptera Aphididae Aphis glycines (soybean aphid)
Species 2: Coleoptera Chrysomelidae Cerotoma trifurcata (bean leaf beetle)

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