Monday, December 11, 2006 - 10:35 AM

Managing bean leaf beetles and bean pod mottle virus in soybean with a seed-treated neonicotinoid and a foliar pyrethroid

Jeffrey Bradshaw,, Iowa State University, Dept of Entomology, Room 4 Insectary, Ames, IA

Bean pod mottle virus causes qualitative and quantitative damage to soybeans and is efficiently transmitted by the bean leaf beetle, Ceratoma trifurcata (Förster). Five (2002) and six (2003 and 2004) potential strategies (seed treatment, early-season foliar insecticide, mid-season foliar insecticide, early- and mid-season foliar insecticide, seed treatment plus foliar insecticide, and a seed treatment plus and early-season foliar insecticide [2003 and 2004]) for managing bean leaf beetles and bean pod mottle virus were evaluated. The current management strategy in Iowa recommends one early and one mid-season Warrior (lambda-cyhalothrin) (2.5 fl. oz./arce [29.9 ml/hectare]) application. Seven treatments were used: Cruiser, Warrior (late May), Warrior (early July), Cruiser plus Warrior (late May), Cruiser plus Warrior (early July), Warrior twice (late May and early June), and an untreated control. The effectiveness of these treatments was measured by comparing beetle populations, percent of virus incidence in soybeans, and seed quality and yield. In general, based on cumulative beetle abundance, the Cruiser treatment (by itself) and the Warrior treatment (late May) had 33.4 and 7.6 fewer beetles, respectively, relative to the untreated control. Apparently, early-July treatments had a marked impact only when the population was large (i.e., > 800 beetles in the untreated control).

Species 1: Coleoptera Chrysomelidae Cerotoma trifurcata (bean leaf beetle)

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