Improving crop risk assessment tools for bertha armyworm

The Challenge

Bertha armyworm continues to cause millions of dollars in crop losses in canola. The current pheromone-based monitoring program was developed in the 1980’s and although it has served the industry well, canola acreage has expanded drastically since.

The Project

Update the current monitoring program by investigating optimal trapping density for outbreak predication to validate the forecasting model, determine if trap height affects trapping efficiency, and investigate trap modifications to reduce bumblebee catch.

The Results

The current survey and forecasting model fared well overall, with some adjustments required. Traps give a general risk assessment for the area, not per field. More traps are required on low risk years to understand where break-outs will occur. Traps were highest when placed in an area where the previous year had higher concentration of canola. There was no benefit seen in changing the trap height, but when the opening and closing of traps were used to decrease bumblebee attraction, it negatively impacted the number of moths caught for the survey.

Grower Benefits

Better understanding of the risk for a bertha armyworm outbreak in grower area – but does not eliminate the need for in-field scouting. Traps can have high moth catch, but fields can still be well below threshold larval density to warrant spraying insecticide, with large variation between fields.