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Hill and Furrow

Black Cutworm Flights Not 'Following the Rules' in 2016

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).

In recent years at the NWIARDC cutting dates have ranged between May 18 and June 6. In 2016, although significant flights were detected both south and north of the NWIARDC, a 'significant flight' never did occur at the NWIARDC (Figure). This does not mean that BCW moths did not lay eggs in the region or that scouting is not warranted. Multiple significant flights have occurred in many regions of the state, indicating that there may actually be a longer window in 2016 in which potential injury may occur.

A recent Bulletin article written by Kelly Estes provides a good summary of the most vulnerable corn growth stages, the influence of weedy fields on egg laying, damage thresholds and rescue treatments and Bt traits for BCWs.