Bean pod mottle virus ecology and management in Iowa

Abstract

Bean pod mottle virus (BPMV) is a new disease problem for North Central states soybean (Glycine max (L.)) growers. The bean leaf beetle, Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae), is the primary BPMV vector. The main objectives of this research were to understand BPMV ecology and explore possibilities for management. Bean leaf beetle, Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae), flight capacity was measured and seventy-one percent of beetles flew 301 m. The mean of flights <51 m was 11 m. The farthest flight made by an individual beetle was 4.9 km. A survey of Iowa counties confirmed BPMV was present throughout the state. In 2002, populations of the bean leaf beetle reached the highest abundance recorded in 14 years. Three BPMV primary inoculum sources in Iowa were confirmed. Seed transmission of BPMV was 0.037%, 1.5% of overwintered bean leaf beetles transmitted BPMV, and Desmodium canadense (L.) was identified as a naturally occurring host. Application of lambda-cyhalothrin (Warrior®) (Syngenta, Wilmington, DE) after soybean emergence and again as first-generation bean leaf beetles emerged, reduced beetle densities for four and seven weeks, reduced BPMV field incidence by 26% and 27%, and reduced seed coat mottling by 10% and 19%, at locations in central and northwest Iowa respectively. Yield was 440.48 kg/ha (6.5 bu/acre) higher in the early followed by mid-season insecticide treatment at the northwest site. Four planting dates and two soybean cultivars were examined in relation to BPMV incidence. In 2000, the lowest BPMV incidence occurred in the third planting date, but the incidence was not significantly different than in the other planting dates. For all years, yield was occasionally highest (although not significantly) in the third planting date and lowest in the last planting date. In 2000, seed coat mottling was