Western bean cutworm complete one generation of egg, larva, pre-pupa, pupa and adult per year. Western bean cutworm adults (moths) are strong fliers, and are known to travel several miles. After mating, females deposit their eggs on the top surface ofcorn leaves in the upper one-third of the plant. Eggs hatch in 5 to 7 days, and larvae feed for 3 to 5 weeks as they develop through five instar stages. In early to mid-September, larvae complete their growth, stop feeding and drop from the ear to the ground. They then burrow into the soil and construct an earthen cell for overwintering.

Trapping and scouting

  • Pheromone traps can be used to determine when and where to scout for adult egg laying. As soon as the first moths appear, immediately begin scouting fields. Look for eggs and larvae on the upper leaf surface in the upper part of the plant. Sample 100 plants by checking 20 consecutive plants in five areas of the field, or 10 consecutive plants in 10 areas of the field. In variable fields, or with more hybrids planted, sample more areas of the field.

Insecticide use

  • When 8% of plants have an egg mass or young larva in the tassel, an insecticide application should be considered. This low threshold is necessary because larvae move between plants. Application timing is critical and multiple treatments may be needed.

Best management practices

  • Plant resistant hybrids to provide in-plant protection against western bean cutworm and eliminate the need for intensive scouting.

Photo: Frank Peairs, Colorado State University, Bugwood.org

For additional information, contact your Pioneer sales professional or visit pioneer.com.