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Issue No. 20, Article 2/August 10, 2007

Root Injury Evaluations Complete, Preliminary Results to Be Shared Next Week

On August 7 we completed our second round of root injury evaluations from DeKalb, Monmouth, and Urbana. In next week's Bulletin (issue No. 21), we intend to share the preliminary root rating results. This year, injury was most intense at Urbana, with nearly three nodes of roots (2.74) destroyed in the primary check (control) by mid-July. Root injury in Monmouth was least intense, with just greater than 1 node of roots destroyed in the check. At DeKalb, root injury was intermediate among the trials, with slightly more than two nodes of roots (2.18) pruned in the check. Considering the reports of lower western corn rootworm densities across the state this summer, we were pleased to see this level of injury in our experiments in order to adequately challenge the various Bt hybrids, soil insecticides, and seed treatments in our trials.

By early August, the level of root regeneration was impressive at the Urbana site. Rating the roots required using a knife to cut away large amounts of root tissue in order to adequately assess the level of pruning on the inner nodes. In areas of the state where soil moisture was plentiful this season and corn rootworm pressure was heavy, lodging may not have occurred due to high levels of root regeneration. Conversely, under very dry conditions, plants may not have lodged due to the very hard soil. Unless excessive lodging and goosenecking of plants occurs, most producers will overlook root injury, even though it may present.

Severe corn rootworm injury and root compensation, August 7, 2007, Urbana, Illinois (University of Illinois).

We look forward to sharing the full complement of root ratings next week.--Mike Gray

Mike Gray

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