Western Rootworm in Corn

The Western Corn Rootworm (WCRW), Diabrotica virgifera is a major corn pest in the mid-west and eastern North American and is now confirmed as active in the central and eastern Fraser Valley in August 2016. Surveying revealed varying levels of infestation in fields of both silage and sweet corn. It has also be confirmed in a neighboring Dahlia flower crop adjacent to a corn field.

The life cycle is one generation per year with eggs being laid in established corn in the late summer in soil cracks. The eggs overwinter and hatch in the spring. The larvae feed on the newly planted corn roots for about a month before they pupate. The adults then emerge in July. The adult beetles feed on corn foliage and pollen and mate. They are active fliers so can move easily from plant to plant. The females feed for about two weeks and then lay their eggs in the corn fields and the cycle starts again. Adults live for about a month.

Damage from the early spring larvae feeding on the corn roots will decrease your plant growth and may cause full or partial lodging of your crop and reduced tonnage. The adult beetles feeding on the silks affect cob fill and contaminate the crop which is especially a concern with sweet corn. Adult beetles feeding on flowers such as Dahlias affect their overall marketability.

If you see this pest in your corn or flowers, management may be necessary. Management includes: crop rotation out of corn every 2-4 years, use of seed treatments, or the use of in-furrow sprays at planting, and / or foliar sprays for adults in July – August. Your sales rep can assist with treatment and chemical options for control if you suspect you have this pest in or near your corn fields.

Photos and technical data courtesy of Tracy Hueppelsheuser and Susan Smith of BC Ministry of Agriculture.