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Hill and Furrow

Black cutworm trap: significant flight in fewer than 24 hours!

In cooperation with Kelly Estes of the Illinois Natural History Survey, every April personnel at the Northwestern Illinois Agricultural Research and Demonstration Center (NWIARDC) maintain a pheromone trap to monitor black cutworm (BCW) moths. Pheromones, or the sex hormones that are produced by female BCW moths, are impregnated into small rubber lures that are placed in the center of a sticky surface in a triangle shaped trap (Figure). These BCW pheromones attract male moths that are looking for a mate. Unsuspecting males then fly into the trap and become stuck on the sticky surface. Personnel check the traps regularly, identifying, counting and removing the moths from the sticky surface (Figure).

BCWs do not overwinter in Illinois, but fly north each growing season along with major weather systems. When a 'significant flight' has occurred, or when nine or more moths are trapped over a 2-night period, degree days - which are based upon historical temperature trends and their effect on BCW developmental milestones – are used to project a potential cutting date. Cutting dates can help to better pinpoint when corn damage may begin to occur, and when scouting should likely commence (Figure).

The BCW trap was set up a little later than usual at the NWIARDC as planting had only recently commenced due to wet and cool soil conditions. Traps were set on the afternoon of April 13 and on the morning of April 14, 17 BCWs were stuck to the sticky trap. We reached a significant flight in fewer than 24 hours!

According to the Illinois Climate Network's Insect Degree Day Calculator the cutting date in Monmouth is May 19. The calculator uses historical weather data and information regarding how heat units affect BCW development to determine when larvae will likely be large enough to do significant damage (cutting) to corn seedlings (Figure). Before that time the larvae will feed on leaves, but will be too small to cut plants.

Additional information regarding scouting, injury thresholds and rescue treatments is included on a BCW handout produced by Kelly Estes and others in 2003.

Many of the hybrids planted today produce a Bt protein that has activity against BCWs, however not every Bt trait has activity against BCWs. A Bt trait table produced by entomologists at Michigan State, Texas A&M and The Ohio State Universities can help producers to better understand whether the Bt traits in their corn hybrids have activity against BCWs.