Manage Western Bean Cutworm in Corn Crops

Western bean cutworm (WBC) is native to North America and is a severe pest in several areas of the Corn Belt. Traditionally a pest of the western Great Plains, WBC has moved east into much of the Corn Belt. While populations may vary from year to year, this corn pest is a consistent threat in some corn growing regions.

Identifying western bean cutworm eggs

Egg masses of up to 200 eggs can be laid in the upper plant leaves and mature quickly over a few days. It is common to find multiple WBC larvae feeding per ear because they are not cannibalistic (unlike corn earworm). WBC is one of many late season pests that can reduce the quality of your corn, so make sure it’s on your scouting radar. This insect can damage corn ears leading to yield loss, infections and mold, resulting in a docked profit when you take your corn to the elevator.

Western bean cutworm scouting and control

To help prevent pest pressure, scout pre-tassel and freshly tasseled fields for large, white egg masses on the upper third of plants. Infestations of WBC are often patchy and may occur over a span of several weeks, requiring multiple scouting visits and creating challenging treatment decisions.

There are multiple options for scouting, which include pheromone traps, using degree days to predict moth emergence, black light traps and actual scouting of corn plants. When scouting corn plants, check at least 20 plants in a minimum of 5 areas in each field for egg masses to make sure your analysis is accurate.

Egg masses can be hard to find. To help detect WBC, hold corn leaves up to the light and look for shadows from egg masses. Inspect the upper 1/3 surface of plant leaves for eggs. Eggs will be grouped into 15 to 50 individual eggs, laid in flat, irregularly shaped masses. Each egg will be about the size of a pin head. Eggs darken as they mature, changing from white with a thin red ring to brown, purple and eventually turning black before hatching. Egg color can help predict egg hatch and proper timing of foliar insecticides. This is important as timing of insecticide treatments can be difficult due to moth flights and egg laying spread over time, resulting in multiple hatch timings.

Proper timing of insecticide application is critical, as larvae will quickly migrate to developing kernels within the husks after hatch. The Ohio State University advises applying an insecticide if 8% or more of your crop contains eggs or larvae. Insecticide treatments should be made while eggs are hatching to control outbreaks. After larvae enter the ear, they are protected from insecticides, making delayed applications ineffective. 

Plant damage from western bean cutworm

Upon egg hatch, young larvae feed mainly on pollen within tassels and eventually move down into developing silks. Once pollination is complete, WBC will quickly move inside the ear husk and feed on developing kernels. Holes in husks are often visible from entering and exiting of ears. Larval feeding affects corn yield and reduces grain quality through damaged kernels and resulting mold and mycotoxin development. Kernel quality degradation can negatively affect the price of grain and can be potentially harmful to livestock.

Protect your corn hybrids from western bean cutworm

If your field has a history of WBC, consider selecting a Golden Harvest^® hybrid that contains the Viptera™ trait, which is the only trait available today that effectively controls WBC. Viptera controls 13 above- and below-ground insects, including WBC, to reduce ear damage that can lead to mold and mycotoxins. It is the best option on the market to consistently limit damage and protect grain quality. By controlling major leaf-, stalk- and ear-feeding corn insects, including WBC, Viptera trait stacks offer better crop stand and lower levels of disease, resulting in increased yield and profit potential. Learn which Golden Harvest hybrids include the Viptera trait by entering relative maturity needs or a specific hybrid name in our online product finder.

Contact your Golden Harvest Seed Advisor with questions or for additional agronomic insights.