Evaluating root injury and maize yield for a seed-blend targetting corn rootworm larvae

The seed-blend concept has been developed by seed companies to simplify the often confusing requirements associated with planting refuges for Bt maize hybrids. These products combine both Bt seed with toxins targeting corn rootworm larvae and refuge (non-Bt) seed into a single bag, ending the need to plant a refuge separately. Seed-blend products have been commercially available since 2010. Since that time, new seed-blend products continue to join the marketplace and are likely to increase in popularity due to their convenience at planting time. In 2011, we initiated a research project to compare the level of protection against corn rootworm larval injury provided by a rootworm Bt hybrid, a seed-blend, and a soil-applied insecticide. Our results indicate that all of these products experienced less larval injury than the untreated check. Additionally, adding the soil-applied insecticide to either the rootworm Bt hybrid or seed-blend did not improve root protection or yield. When evaluating root protection offered by the seed-blend, we were particularly interested in how Bt plants performed that were immediately adjacent to refuge plants. While the refuge plants did experience some larval injury, the adjacent Bt plants continued to provide excellent protection. This experiment will be continued in 2012, and data will be presented from both years of this research project.