No. 22 Article 1/September 2, 2005

Preliminary Root-Evaluation Ratings Available for DeKalb and Urbana Corn Rootworm Product Trials

The preliminary root-rating results have been analyzed for two of our corn rootworm product efficacy experiments (DeKalb and Urbana; Table 1). Data from a third trial (Monmouth) are still being evaluated. We look forward to sharing the results from the Monmouth study in our next issue of the Bulletin. As you review these data, please keep in mind that our studies are conducted on corn plots that have been planted into a trap crop (late-planted corn in 2004 interplanted with pumpkins). By using a trap crop, we purposefully place corn rootworm products under intense pressure. Although it is less common to witness root injury as intense as occurred in our experiments, many of us have observed severe root damage and lodging in producers' fields through the years, including this season. We believe the results from our trials better enable producers to make the most informed choices regarding product selection for corn rootworms.

Root-injury ratings in our checks at DeKalb and Urbana were nearly identical: 2.37 and 2.32, respectively. These root-rating averages indicate that 2-1/3 of nodes were destroyed on plants within our check treatment at each site. A preliminary review of these root-rating data from DeKalb and Urbana suggests the following:

Overall, these results are somewhat similar to what we have observed in previous years for a number of the treatments. Despite the very dry soil conditions this summer, the granular products provided very good to excellent root protection. Corn rootworm products will continue to be challenged more intensively as planting dates are pushed back earlier and earlier in the spring. The importance of proper calibration and incorporation cannot be overemphasized for the soil insecticides. In an upcoming issue of the Bulletin, we will share the root-rating results from the Monmouth experiment and offer additional information on late-season brace root feeding in the YieldGard rootworm treatment that we've observed in both 2004 and 2005 in some of our experiments.--Mike Gray, Ron Estes, and Kevin Steffey

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