Western bean cutworm flight in central Michigan is up from recent seasons

Dry bean growers should be aware of this increased flight, but don’t panic.

August 3, 2018 - Author: Frederick Springborn

WBC moth
Western bean cutworm moth resting in dry bean canopy. All photos by Fred Springborn, MSU Extension.

Peak flight of western bean cutworm occurred largely over the week of July 21-28, 2018, in Michigan’s Montcalm area. There are still a significant number of moths being captured in some pheromone traps as of Aug. 2.

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, plus…
  • Neighboring pre-tassel corn fields have egg masses, plus…
  • Blossom and pod feeding observed in dry beans.

From my own observations and from what local agribusiness scouts are reporting, egg masses are few and small in pre-tassel corn. This may be an indication that the number of eggs produced per moth may be much lower than what we experienced in the 2009 and 2010 growing seasons. Remember, it is not the moths that feed on dry beans, it is the larvae that hatch from the eggs produced by the moth. Lots of moths producing few eggs may be no more of a threat than a small number of moths producing big egg masses.

WBC Feeding
Western bean cutworm larvae feeding on a bean pod in 2010 when populations were near an all time high.

Check fields periodically for signs of western bean cutworm larval blossom and pod feeding this week and through August. In particular, 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.

More information on the biology of this pest as well as helpful pictures can be obtained at Western Bean Cutworm in Michigan: Quick Recommendation Sheet for Dry Beans from Michigan State University Extension.

Montcalm area trap counts 2018

Nearest town

July 20

July 27

Aug. 2

Total

Stanton 1

14

24

18

56

Stanton 2

18

41

5

64

Sidney

171

205

61

437

Sheridan

231

183

73

487

Greenville 1

62

67

26

155

Greenville 2

143

241

96

480

Trufant 1

55

62

39

156

Trufant 2

57

57

29

143

Coral

91

227

37

355

Tags: msu extension, western bean cutworm


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