Thirty-three sites reporting this week. European corn borer (ECB)-E was caught at six sites and ECB-Z was caught at seven sites. Seven of the ten sites reporting corn earworm (CEW) were over threshold, indicating a need for a spray, please see the chart at the bottom of this page to determine the correct spray interval for your field. Fall armyworm (FAW) was caught at eight sites and Western bean cutworm (WBC) were caught at seventeen sites this week.

WBC flight usually peaks the first week of August. Below is a map created by Dan Olmstead, NEWA coordinator, showing the estimated WBC flight completion based on Hanson et al.

Western bean cutworm estimated flight completion on 7.22.19.

Summary of Hanson et al. (2015) by Dan Olmstead:

A group from University of Minnesota published a revised method for predicting western bean cutworm flight periods in 2015. The older literature, commonly referred to as the ‘Nebraska method’ was published in 1976. The new method, referred to as the ‘Hanson method,’ noted WBC range expansion into Northern and Eastern US regions where suitable temperatures before the historical model start date of May 1 may occur.

The Minnesota group used historical WBC black-light trap data from Nebraska to compare actual 25% flight completion dates with predicted values derived from a variety of candidate models having different lower and upper development thresholds using both simple and modified sine wave degree day calculations.

The best fit model proved to be one using a lower threshold of  3.3°C (38°F), an upper threshold of 23.9°C (75°F) and a simple daily degree day calculation.

To determine the estimated flight prediction of the sweet corn sites, use the degree days in the table below. Degree days were calculated using a base 38°F but not the upper threshold of 75°F. The degree days are therefore overestimated a bit.

Dry Bean Western Bean Cutworm Alert
7.23.19
Marion Zuefle, NYS IPM Program
(Alert modified from Carol McNeil)
(Information and photos from T. Baute, OMAFRA)

This year we are monitoring eight WBC traps placed next to dry bean fields. The location of the traps are given in the image below. Dry bean growers should scout adjacent corn  for WBC eggs and larvae when cumulative trap catch reaches 50 moths. Peak WBC flight historically occurs the first week of August. All dry bean growers should begin scouting pods for WBC feeding about 10 days after peak flight regardless of cumulative trap catch, and should continue to scout for three weeks, especially if damage has been seen in recent years.

Check 10 random spots in a field, 5 plants per spot. Inspect all the pods on the plants looking for holes. Surface feeding can be caused by other insects. WBC will mine directly into the pod and will often feed on the seed inside. European corn borer will also feed inside the pod and would most likely still be present. If there is damage going directly into the pod and seed but no larva present, it is quite possibly WBC. During the day WBC larva are not actively feeding in the pod, instead they drop to the soil and will remain there until night. Fresh damage will be green, not brown.

If you have questions contact Marion Zuefle at mez4@cornell.edu or 315-787-2379.

This project is funded by the NYS Dry Bean Industry.

Location of WBC traps near Dry Beans in 2019.