European corn borer, corn earworm, and,fall armyworm trap catches are low this week at many (not all) locations.  Western bean cutworm are being caught at all locations this week, with numbers getting into the low 20’s in Kirkville.  Much higher numbers have been reported in northern NY, and egg masses have been found.  This may be the week of peak catch for WBC, so it’s time to get out and scout for egg masses and newly hatched larvae.  Late whorl and early tassel-emergence stage fields are most at risk.  Egg masses are relatively easy to see; they can be found on the upper leaf surface near the emerging tassel, or on the tassel.  Eggs are round with a sculptured pattern on the surface that can be seen with a hand lens.  Eggs are white when first laid, turning purple just before hatching.  See the western bean cutworm fact sheet and ID card for photos of egg masses and larvae.

Thresholds for western bean cutworm have not yet been established for NY.  The following information on western bean cutworm management is from Elaine Roddy, OMAFRA Vegetable Crop Specialist for Sweet Corn, Beans, Peas, Cucumbers, Melons, Squash, Pumpkin, Zucchini and Asparagus. Soils, Fertility, IPM and more.  Ridgetown, Ontario.

Sweet Corn: Crops at the pre-tassel to full tassel stages are at the highest risk of WBCW infestation. Inspect a minimum of 100 plants across the field.  Focus on the top three-to-four upper leaves of the plant. Look for egg masses and young larvae. Egg masses are initially white and turn purple when they are within a few days of hatching. Newly hatched larvae spend a few days feeding on the tassel before moving down to the ear. Use a control threshold of 5% eggs or larvae and time the spray applications to target the newly hatched larvae.  Most insecticide sprays used to control European Corn Borer will also control WBCW.

Snap Beans: To date we have not seen significant feeding of WBCW in commercial snap beans in Ontario. However, when research plots are inoculated with egg masses, feeding damage can be significant, indicating that this is a potential pest of commercial fields.

In dry beans, the WBCW eggs are often inconspicuous and the larvae feed only at night. As a result, scouting for pest activity is very difficult.  Keep track of the pheromone trap counts in your area to determine for peak moth flight.  Peak moth flight indicates when peak egg laying takes place. Pod feeding typically occurs 10-20 days after peak moth flight.  If possible, scout adjacent field corn or sweet corn fields to help gauge the potential risk in a snap bean crop.  As with sweet corn, sprays used to control European Corn Borer will also control the Western Bean Cutworm.

Trap catches for the week of 7/17-24/12