Western Bean Cutworm in Edible Beans

Western Bean Cutworm (WBC) are active now in both corn and edible beans fields. While we do not have an action threshold specific for treatment of WBC in dry edible beans, farmers can scout nearby corn fields and consult the available resources listed below.

Infosheet: WBC Management Strategy for Dry Edible Beans

Corn Pest Coalition -WBC Trap Network with Interactive Maps

Foliar Insecticides Registered for WBC Control on Dry Edible Beans


Western Bean Cutworm in edible beans in 2016 (J. Bruggeman UGRC)
Western Bean Cutworm in edible beans in 2016 (J. Bruggeman UGRC)

The following information is taken from a 2015 post on Field Crop News, written by Tracey Baute. You can search the website for other articles on WBC.

For dry beans, it is highly unlikely that you will find eggs or larvae no matter how diligent you are at scouting.  In dry beans, the larvae are active at night and hide in the soil during the day.  You are much better off spending your time looking for the first signs of feeding holes in the pods.  Pod feeding is expected to start approximately 10 to 20 days after peak flight.  Effective control can still occur then, as long as pod feeding is spotted early and dealt with.

Dry bean fields planted on sandy soils and in areas of known hot spots (Thamesville to Strathroy and Tillsonburg/Simcoe) are at higher risk. Fields bordering corn fields that have reached threshold are also at risk, especially once corn is beyond the pre-tassel stages.

Action Threshold for Dry Beans: If WBC has reached a threshold in the neighbouring corn field, adjacent dry bean fields are likely at risk, especially if the corn fields have passed the pre-tassel stage and moths are still actively flying, as indicated by the pheromone traps. If entry holes are observed in the pods, an insecticide application is necessary.

Since WBC exit and enter new pods each night, foliar insecticides can still work at controlling the larvae. Select insecticides that have some residual and pay attention to pre-harvest intervals.  Recommended insecticide options are available here (the same link as above): Foliar Insecticides Registered for Western Bean Cutworm Control on Dry Edible Beans in Canada. Spot treatments may be effective if injury is concentrated to one area of the field.

WBC damage in dry bean pods in Ontario in 2014 (J. Smith, UGRC)
WBC damage in dry bean pods in Ontario in 2014 (J. Smith, UGRC)