The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) has begun its annual corn rootworm beetle survey.
As of August 8, crop scouts have sampled approximately 25% of the 230 survey sites across Wisconsin. While it is still early to draw conclusions about this year’s corn rootworm pressure, preliminary findings suggest that beetle counts remain mostly below the economic threshold of 0.75 beetles per plant. Of the 63 grain corn fields surveyed so far, 47 fields (75%) reported low beetle counts ranging from 0.0 to 0.4 beetles per plant. Five sites (8%) showed moderate counts between 0.5 and 0.7 beetles per plant.
However, the survey also identified 11 sites (17%) where beetle counts exceeded the threshold, with individual fields in Dane, Grant, Iowa, Lafayette, and Pierce counties recording exceptionally high averages of 2.6 to 7.1 beetles per plant. These above-threshold counts are a strong indicator of potential larval root injury risks for the 2025 corn-growing season, especially in continuous corn systems.
As beetle emergence continues, DATCP advises corn producers to remain vigilant. Corn rootworm adults are likely to migrate from early silking fields to later-planted fields, increasing the potential for higher beetle pressure. Farmers are encouraged to conduct their own field scouting to assess beetle populations and anticipate next season’s risks.
The DATCP survey is expected to conclude by the end of August.
