Why and how to trap for western bean cutworms in corn and dry beans

Trapping, scouting and mapping western bean cutworms in Michigan corn and dry beans.

Its mid-June—time to think ahead to western bean cutworm emergence. Given the amount of western bean cutworm damage and quality issues in corn last season, people are more interested than ever in trapping for this insect.

My Michigan trap data this year will be posted weekly at Western Bean Cutworm Trap Network.

Why trap for western bean cutworm in corn?

The purpose of trapping is to time scouting. Trapping determines the week of peak catch with the highest moth flight. Egg mass scouting should start after peak catch, targeting pre-tassel fields in your area.

After last year’s failure of Cry1F corn, I now recommend scouting any pre-tassel fields, Bt and non-Bt hybrids. Once you learn to identify egg masses, scouting is not difficult. The threshold is an accumulated 5 percent of plants with egg masses (i.e., add percent infestation over two to three weeks of scouting).

Why trap for western bean cutworm in dry beans?

Trap catch is often used to determine the need to treat. Unfortunately, there are no specific thresholds for moth counts or larval damage in beans, just our experience over the years with flights and resulting pick.

Take note if a trap near dry beans accumulates 50 or more moths. Scout this field for pod feeding after peak flight, and treat if feeding is found. If more than 150 moths are accumulated in a trap near dry beans, Michigan State University Extension usually suggests treating simply based on this high trap catch.

Western bean cutworm trapping supplies

For trapping supplies, see the “Great Lakes IPM Insect Monitoring Supplies for the Professional Grower” 2017 catalog, or call them at 800-235-0285.

  • The trap = “Universal moth trap.” Use green (IPS-G004) or clear (IPS-CLEAR) buckets. See page 9 in the Great Lakes IPM catalog.
  • Trece pheromone lures, at least three lures per trap (change every two to three weeks). Save extras in the fridge for 2018. TR-WBC 3406 pack of 25 lures, $44. See page 13 in the Great Lakes IPM catalog.
  • Hercon vaportape = fumigant strips to kill moths in buckets. I attach a piece of the fumigant strip using glue or tape to the inside of the bucket so I don’t dump it out accidently. HC-8500-25, n= 25 strips in a pack, $6. See page 9 in the Great Lakes IPM catalog.

Entering data and mapping for western bean cutworm

The Canadian Corn Pest Coalition in Ontario has maintained a western bean cutworm trapping site for Ontario and Quebec for several seasons. To see how the Canadian Corn Pest Coalition displays trapping data, view the interactive western bean cutworm trap maps. Hit the play/arrow icon and the moth flight for the 2016 season plays out as colored dots. It’s very cool.

This year, the Canadian Corn Pest Coalition kindly added Michigan to their network. To be a trapper and enter data (on Mondays for the previous week), you must join the network. Links for specific instructions for making a log in, adding trap locations and entering data are on left side of the Western Bean Cutworm Trap Network website.

My locations and the first counts should be on the map the week of June 18, 2017. If you are trapping in Michigan, consider contributing your numbers as well so we can cover the state. If you would rather call-in numbers to my office and have me add them for you, email me at difonzo@msu.edu.

Dr. DiFonzo’s work is funded in part by MSU’s AgBioResearch.

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