No. 18 Article 3/July 22, 2005

Assessing Product Performance for Corn Rootworms: Checks Are Vital

During the past week, we continued to evaluate the severity of corn rootworm larval injury in several experiments located near Urbana. The level of pruning in some trials remained very impressive. As mentioned in the Bulletin last week (issue no. 17, July 15, 2005), we are beginning to observe root regeneration on many of the plants we rate for injury. It thus may be worthwhile during the next few weeks to evaluate the effectiveness of your chosen product. Root regeneration will only make it increasingly difficult to assess larval injury. To evaluate product performance most effectively, one or more check or untreated areas in your field are very important. Some producers may assume if lodging does not occur that their method of corn rootworm larval control has worked satisfactorily. This assumption can prove wrong, especially in a dry summer such as this one.

If you left a check in your field(s) and have taken the time to evaluate root systems for injury in both treated and untreated areas, we would be interested in receiving your assessment of product performance. For those who have planted a transgenic corn rootworm hybrid, how does rootworm injury in the refuge compare with the bulk of the field? Please refer to issue number 14 (June 24, 2005) of the Bulletin for a full description regarding the root-evaluation process. We look forward to your reports.

Severe corn rootworm injury in the check (untreated) from an Urbana experiment.

Thousands of washed and rated roots from corn rootworm experiments located near Urbana.

--Mike Gray

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