Cereal leaf beetle, Oulema melanopus (L.) (Coleoptera: Chrysomelidae), attraction to oat plantings of different ages

The cereal leaf beetle (CLB), Oulema melanopus, a serious pest in oats, barley and wheat, is a relatively new pest on the west coast of North America. To determine if adults showed a preference for oat stands of different ages, we examined adult and egg densities in four sequentially planted oat stands in the Willamette Valley, Oregon, in 2005 and 2006. Adults moved from earlier to later plantings (from older to younger oats) during the growing season, particularly once the flag leaf had emerged in earlier plantings. In 2005, the seasonal pattem in egg counts tended to match that of adult counts in the first three oat plantings. The egg to adult ratio was greater in the earlier planted (older) oats, particularly the first planting. The egg to adult ratio was more variable in 2006. Adults spent the most physiological time (degree—days) in the second oat planting, and total egg numbers were highest in the second and third plantings. Data suggest that delayed planting as a trap crop management tool for CLB is complex and potentially ineffective