The 2009 ASHS Annual Conference

Organic agricultural sales increased to a $20 billion in the U.S. in 2008 and continue to maintain momentum despite the economic downturn in the U.S. In the last five years, additional organic seeds have become available to aid compliance with the USDA-National Organic Program requirement that organic producers source certified organic seed/cultivars for their operations. Among the most important production issues for organic sweet corn in the Midwestern U.S. are managing soil fertility and timely pest management. This project investigated cultivar selection from organic and conventional seed and the efficacy of the naturally occurring soil bacterium, Bt (Bacillus thuringiensis kurstaki), for improved pest management of the corn earworm (Heliocoverpa zea). Treatments were applied to the corn ears when 50% were silking, and 2 to 4 days later, using a pressurized backpack sprayer. Results from these four-year trials show great variability in earworm damage, ranging from 0% to 66% damage, depending on the year. Overall performance of organic sweet corn was excellent, with yields ranging from 12,894 to 20,790 ears/acre. Earworm damage varied by cultivar but there were no differences between organic and conventional cultivars. There was a trend toward less earworm damage in the organic Bt treatments, but the damage was not significantly less than the control (no spray). These experiments were conducted from May to July when warm air and soil temperatures ensured rapid emergence and growth. Organic sweet corn destined for earlier or later markets may encounter increased pressure from corn earworm populations.