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Crop Scout Alert: Significant Black Cutworm Moth Activity

Crop Scout Alert: Significant Black Cutworm Moth Activity

Black cutworm moth activity has started across some areas in the Midwest with significant moth counts reported in some counties in IL and IN. As of 04-23-19 Madison and Warren counties in Illinois have reported significant black cutworm moth flights with projected cutting dates of May 10th and May 21st respectively. In Indiana Adams, Allen, Clinton, Fayette, Fountain, Hamilton, Jay, Montgomery, Putnam, Shelby, Sullivan, Tippecanoe and Tipton have also reported significant moth captures. Iowa has not yet reported any significant flights but trapping has started and a few moths have been observed already. Following these updates is very important as they provide some guidance on scouting activities and when degree day accumulation for this pest should be started. 


The cutting damage to corn (when the base of seedlings is clipped at about soil surface) begins when 300 pest degree days have accumulated following the first significant moth capture of 9 or more moths for two consecutive nights (biofix). The degree days are calculated for a 24-hour period and accumulated (summed) over a period of time using the formula: [(maximum daily temperature + minimum daily temperature)/ 2] -50. This is how the projected cutting dates for Madison and Warren counties have been calculated.

Black cutworm moths do not overwinter in the Midwest, but instead migrate into the area in April and May on storm fronts and prevailing southwesterly winds. Adult moths are nocturnal, large bodied, and dark grey in color, with a black dagger-like marking on the outer forewing (below, left).  Females lay eggs in masses of 10-30 near food sources such as grassy habitats, low areas of fields, soybean residues, and areas of winter annual weeds. BCW larvae are gray to nearly black in color with a greasy appearance, a pale band along the top of their bodies and paired spots of uneven size along the sides. (below, right)


Keep your eyes open as the crop gets planted. For more up to date information on insect pest activity and disease reports follow us on Twitter @GMK_Agronomy. Happy Scouting!

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