Western Bean Cutworm- Plan to manage for 2022

This year as we moved west of highway 281 in Nebraska and Kansas, the western corn belt saw a huge pressure from an infamous pest- western bean cutworm. I have heard of fields in western Kansas where 85% of the plants had an egg mass and have personally seen fields in which 65% of the corn plants had an egg mass in the upper canopy. Let’s review this pest and consider management options for 2022 and beyond.

First, what is a western bean cutworm? The western bean cutworm moth emerges in July, where it mates and begins to lay eggs in the upper canopy of corn plants until mid-august. Eggs hatch, crawl down the leaves and begin to feed on ear tips until mid-September.

This year in the western corn belt, due to lack of a hard freeze at 5-10 inches in the soil, many WBC prepupae survived the winter and were able to produce offspring in 2021. Although we had freezing air temperatures for most of February, soil temperatures barely dropped below 25 ^oF (chart below).

So, what can be done to manage this pest? WBC is a member of the Lepidopteran family of insects, which are controlled by the Bt trait VIP3A, commonly known as Leptra. Planting an AML hybrid is a surefire way to control WBC. However, many acres in the corn belt are under corn-on-corn or continuous corn management, which typically warrants the use of a Bt protein to control corn rootworm larvae below-ground. In this scenario, WBC won’t be controlled by the trait and could call for use of an insecticide. After tasseling, cornfields should be scouted to count the number of egg masses per 100 plants. Fields that have 5-8% of plants with an egg mass in the upper canopy typically call for an insecticide application.

Agronomist Contact Info:

Name: Phil Swantek

Title: Product Agronomist

Email: p.swantek@hoegemeyer.com

Be sure to check out our website at therightseed.com for more information!

Sources

• https://cropwatch.unl.edu/2021/how-have-cold-february-temperatures-affected-insect-overwintering-nebraska
• https://cropwatch.unl.edu/2020/scouting-and-treatment-recommendations-western-bean-cutworm