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Western Bean Cutworm

Description

Western bean cutworm is a recent immigrant into NYS and is starting to become an economic pest in some counties in NNY and WNY. This insect was historically found in the western Corn Belt where it is a common pest of dry beans and a sporadic pest of corn. Starting in the year 2000, economic damage from this pest was found on corn in Iowa and Minnesota. In subsequent years, this pest has continued to rapidly spread eastward, with the first detection in WNY in 2009. A statewide pheromone trapping effort between 2010 and 2016 has documented the moth continuing to spread eastward across the state and an ever increasing overwintering population.

The adults are mostly dark brown and black, with three characteristic markings that distinguish them from other moths: (1) a white stripe on the top edge of the forewing, (2) a light brown, tan colored dot, and (3) a comma or crescent-shaped mark behind the dot. The adults emerge in late June–early July after fully grown larvae overwinter inside soil chambers in the soil 3–8 inches deep. Mid-flight of the adults usually occurs in mid-July, with adult flight ending by mid to late August. There is one generation per year. Eggs are usually laid on the uppermost portions of the flag leaf in egg clusters averaging 50 eggs per cluster. Eggs are white when laid and then turn purple when just about ready to hatch.

Larvae are tan in color and can be identified by two broad stripes immediately behind head. In addition, since WBC is not cannibalistic, larvae usually occur in groups feeding directly on the developing kernels. The damage caused by larvae feeding on kernels also increases risk of subsequent infection by ear mold fungi, including those capable of producing mycotoxins.

Management

Economic populations of WBC are starting to be reported across the NNY counties.  Increasing moth populations are being recorded in WNY and economic populations are expected in future years.  The two oldest BT-cornborer events are not effective in controlling WBC and producers should contact Cornell Extension personnel for the current recommendations about effective WBC-BT events.