Scouting dry beans for western bean cutworms

First detected in Michigan in 2006, the western bean cutworm – a late season pest – can impact the quality and yield of dry beans.

Under the direction of Christina DiFonzo, MSU Department of Entomology, MSU initiated a western bean cutworm trapping network in 2007. This network provides data on the emergence and peak flight of the western bean cutworm. With dry beans, it is important to know what the population of western bean cutworm moths is near the dry bean field. For that reason, pheromone traps are placed near dry bean fields. As few as 150 total moths indicate a large, local population.

Megan Chludzinski, entomology graduate student, offers these tips for scouting dry beans.

  • Monitor pheromone traps – 150 moths total indicates a large, local population.
  • Look for egg masses in nearby corn fields that are at pre-tassel or pollination stage.
  • Seven to 10 days after egg masses are found in corn, scout dry beans for feeding injury. Look for small pinholes in the flowers; small pods will be cut-off at pedicel, larger pods have chew spots or holes. Be patient and examine plants carefully as damage can be difficult to spot.

For Michigan, an insecticide application may be necessary if:

  • Average pheromone trap catch is greater than 150.
  • Nearby pre-tassel corn fields have egg masses.
  • Pod damage is present.

Additional information on scouting and specific recommendations for control of western bean cutworms in dry beans in Michigan can be found in Western Bean Cutworm in Michigan: 2012 Management Recommendations for dry beans.

To follow the progress of the western bean cutworm, visit the 2012 MSU Western Bean Cutworm Trap Network website. More information on western bean cutworms can be found at the MSU Field Crops Entomology website.

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