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The points of contact between Rutgers Cooperative Extension Service and the grower & business communities are the NJ County Agricultural Agents. The agents are a tremendous source of information for both new and experienced growers. Visit your local county extension office.

Tuesday, July 17, 2012

Western bean cutworm found in New Jersey

-Joseph Ingerson-Mahar
We have been anticipating the arrival of this insect pest for a couple of years.  July 16, 2012, one specimen of this moth was found in a blacklight in Hammonton.  It will be sent to the USDA for official confirmation for a state record.
It is a pest of field corn, sweet corn, and popcorn, and dry beans.  However, with its range expansion it may begin feeding on other crops, as well. 

This is a western pest that has expanded its range eastward, much like the western corn rootworm did 25-30 years ago.  WBC was found in most of the North Central states and Ontario by 2008, Pennsylvania in 2009, and Delaware by 2011.  Now WBC has arrived in New Jersey.  It is a pest of field corn, sweet corn, and popcorn, and dry beans.  However, with its range expansion it may begin feeding on other crops, as well.  The caterpillars feed primarily on the corn ears and on the developing pods of beans.  Unlike corn earworm caterpillars, the WBC caterpillars are not cannibalistic and several can be found on a single ear. 
The adult moth can be recognized by the broad light band along the leading edge of the front wing.  Midway along this band there is a single white spot (with dark center) and beyond that a crescent shaped mark. The moth is medium sized, about the same size as corn earworm moths.  There is one generation a year.  Adult flight begins in late June or early July and caterpillars are present to feed on corn ears and bean pods from late July, August and early September.   Egg masses are laid on the leaves of the corn and beans but are harder to detect on beans.   Mature caterpillars will seek shelter in the soil and remain there through the winter and spring, emerging as adults around the end of June. 
Most likely, this pest will be controlled in sweet corn with the usual tassel/silk sprays that are applied for managing corn earworm.  Apparently the caterpillars are susceptible to some strains of Bt corn, but growers should check seed labels to see if WBC is included as one of the pests that are controlled with that strain of Bt.  The larger question will be whether this invasive pest will feed on other crops.
Thresholds for control will evolve, but one extension bulletin (University of Wisconsin) suggests for processing sweet corn a threshold of 4% of the stand infested. 

Joseph Ingerson-Mahar