Corn Earworm Pressure Remains High in MN: New CEW Forecast & Risk updates

Bill Hutchison, MN Extension IPM Program, UMN

August 23, 2016

Unlike the past 2 years, where late-season Corn Earworm (CEW) immigration events have been late to less frequent, we have experienced several significant incoming flights this summer. Moreover, because the southern states that provide our source moths are reporting record high numbers in all key crops (sorghum, cotton, corn), the numbers we are seeing at most of our southern MN locations are above average to high. 

Blue Earth continues to be high mark this year, with numbers in the 500-800/night range; historically, this has been a hot spot. With all data in yesterday, moth flight numbers again increased at Lamberton, Sleepy Eye and Rosemount. Trap location, in relation to sweet corn production area, and silking phenology is also key to understanding CEW trap catch dynamics. To provide the best early and consistent indicator of activity, traps should always be placed near fresh-silking corn, and moved from mature corn (brown silks) to fresh-silking corn when multiple planting dates are involved. As one example, to illustrate the impact of production area at Rosemount, traps located at the high-catch site of 350/night, are near a 100-ac sweet corn field (actively silking) whereas the lower trap catch (50/night) was recorded near smaller sweet corn research plots (<1.5 ac).  

Bottom line: nearly all sites recording CEW trap catch are way above the action threshold of 5/night, and sweet corn, snap bean, tomato and other attractive crops should be scouted carefully, with plans continuing for treatment. 

CEW Trap locations can be viewed at: http://www.vegedge.umn.edu/moth-data/cew-info 

CEW Migration Forecast for MN, Aug. 23rd: then moving east: http://www.insectforecast.com/ (under "Choose a Pest", select Corn Earworm) 

​For more information, see the Midwest Vegetable Production guide: https://ag.purdue.edu/btny/midwest-vegetable-guide/Pages/default.aspx


CEW moths in a Hartstack trap

Close up of a Hartstack trap containing one night of CEW moth catch.