Northern Corn Rootworm

Diabrotica barberi

Northern corn rootworm adult
Northern corn rootworm adult. Photo courtesy of Daren Mueller, Iowa State University. Licensed under CC BY 3.0.
Northern corn rootworms are an extremely destructive pest of corn in the U.S., particulary since they attack corn both as larvae and adults.
The northern corn rootworm adult is approximately 1/4" in length and has a solid yellow-green body, distinguishing it from the related western and southern corn rootworm species.
Photo of adult southern, northern, and western corn rootworms
Photo of adult southern, northern, and western corn rootworms. Photo courtesy of R.L. Croissant. Licensed under CC BY 3.0.
The larva are thin and grow up to 1/2" long. They have a brown head and white body.
Corn rootworm larva
Corn rootworm larva. Photo courtesy of Scott Bauer. Licensed under CC BY 3.0.
Larvae feed on the roots of corn plants, reducing their ability to absorb water and nutrients which can result in significant yield loss, particularly in dry conditions. The weakened roots can also make the plants prone to lodging making harvest more difficult.
Adults feed on corn silks, reducing polination and hence the total number of kernels, resulting in significant yield loss.
Soil applied insectides at planting can be effective at controlling western corn rootworm. Seed treatments can also provide control for low to moderate infestations. Always read and follow all label instructions.
Many Bt traits provide protection against northern corn rootworm.
Because northern corn rootworms can only complete their lifecycle on corn (and related grasses), crop rotation was once an effective control technique. However, some morthern corn rootworms eggs now bypass this technique by remaining in the soil for two years before hatching (and thus skipping the year in which the field is rotated away from corn). Nonetheless, fields with high adult pressure one year will likely have high larval pressure the following year and so rotating away from corn in these fields remains a good management strategy.