Western bean cutworm is alive and well in central Michigan

Frederick Springborn, Michigan State University Extension - August 15, 2019

Dry bean growers and crop consultants should begin scouting for damage this week.

Western bean cutworm feeding — Photo by Fred Springborn, MSU Extension

Peak flight of western bean cutworm occurred largely over the week of July 28 – Aug. 5, 2019, in west central Michigan. This is a full week later than last year and several previous seasons. There were still a significant number of moths being captured in pheromone traps as of Aug. 12.

Several western bean cutworm pheromone traps have passed the mark of 150 total moths captured for the season, but it is important to remember the rest of the guidelines:

Greater than 150 moths captured in pheromone traps.
Neighboring pre-tassel corn fields have egg masses.
Blossom and pod feeding observed in dry beans.

8-15 wbc 4and5 — Photos by Fred Springborn, MSU Extension

From my own observations and from what local agribusiness scouts are reporting, egg masses have been few in pre-tassel corn. With pre-tassel corn abundant throughout the flight period, western bean cutworm may have had lots of corn to deposit eggs upon, which may be diluting the population. Remember, it is not the moths that feed on dry beans, it is the larvae that hatch from the eggs produced by the moth.

Check dry bean fields periodically for signs of western bean cutworm larval blossom and pod feeding this week and through the rest of August. It will take time and patience to scout for this feeding, especially to find it early. You will not see it by driving by a field or flying over it with a drone. Growers of large seed dry beans such as kidney beans should consider an insecticide application if feeding is detected, especially if those beans are heading for a quality-sensitive market. Insecticide applications should begin at least seven to 14 days after peak flight has occurred. Be sure to observe pre-harvest intervals and read and follow label directions.

Montcalm County, Michigan, area trap counts 2019
Nearest town	July 23	July 30	Aug. 6	Aug. 12	Totals
Entrican	5	25	68	55	153
Stanton	16	91	127	4	238
Greenville 1	82	141	103	54	380
Greenville 2	28	35	62	23	148
Sidney	22	69	18	10	119
Trufant 1	54	87	200	60	401
Trufant 2	36	123	87	51	297
Coral 1	29	78	71	19	197
Coral 2	14	105	111	17	247

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).