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C.O.R.N Newsletter 2009-34
     October 6, 2009 - October 13, 2009


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Low Western Corn Rootworm Variant Numbers for 2nd Straight Year
by Andy Michel, Ron Hammond, Bruce Eisley

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Western Corn Rootworm (WCR) Variants are WCRs that will lay eggs in soybean during August and September (the normal oviposition site is corn, which is why we call these "variants"). If these fields are rotated to corn the following year, the first-year corn will be at risk for root damage. Monitoring for this pest is achieved using yellow sticky traps in soybean, with beetles counted every week. If the number of beetles per trap per day exceeds 5, then protection of first year corn is warranted. Ohio State University Extension personnel continued trapping for the WCR variant for the 13th year in a row. The number of fields exceeding the 5 beetles/trap/day threshold decreased, just like in 2008. However, for 2009, none of our fields exceeded threshold, even though we sampled fields with historically high numbers of WCR variant. Most of our fields were not even close to 5 beetles/trap/day, and our average for the entire state was less than 1. Other Midwestern states are reporting similar low numbers.

Why have the numbers decreased for 2 years in a row? There are many intriguing thoughts, including weather factors (cold, wet springs), as well as the possibility of Bt-rootworm corn hybrids having similar effects to that of the European Corn Borer - a wide-scale decline in rootworm populations. However, we do receive reports of first year corn fields that are heavily damaged from the WCR variant, even near fields that were monitored with yellow sticky traps, which suggests that "hot-spots" of WCR variant remain. More data will be needed to make definitive conclusions on the current status of western corn rootworm variant. However, the presence of "variant hotspots" strongly emphasizes the need for individual field scouting, as there seems to be a lot field to field variation.

Readers can subscribe electronically to this newsletter by signing up at http://agcrops.osu.edu/services/email.html. E-mail labarge.1@osu.edu if you have problems subscribing or no longer wish to receive this newsletter.

C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.


Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868

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