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.
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
