The western bean cutworm (WBC) is a relatively new pest to the Northeastern U.S. It migrated from the west, showing up in New York in 2009, and has been found throughout the East Coast since 2017.

Unlike the West, the WBC does not have many natural enemies in the Northeast, making them a larger problem to deal with.

Allen Wilder is the forage agronomist at the Miner Institute in Chazy, NY, where the WBC has “become quite a bit of a pest.” WBCs are “actually the biggest problem in corn,” both sweet corn and grain corn, according to Wilder.

They begin as eggs laid on the plants’ foliage, where they hatch as larvae, then crawl around the plant and eat all over it before settling in the ear tip.

Unlike their name suggests, the WBC is not a true cutworm, but is instead an ear pest. They cause crop damage by making the ear look “gross” and “moldy,” and can even burrow straight through the ear and stalk.

There are limited options available to control this pest. Insecticides can work, but only if applied before the larvae are settled and protected in the ear.

Two traits were previously developed to affect WBCs: CryF1 (a pro-tumorigenic factor that rhythmically modulates DNA repair) and Vip3A (whose gene product shows activity against lepidopteran insect larvae including black cutworm, fall armyworm, beet armyworm, tobacco budworm and corn earworm).

Studies have supported that WBCs are resistant to CryF1 and susceptible to Vip3A. There is very limited data to determine if WBCs impact the resulting corn silage, so the Miner Institute set out to actually test this.

During Miner Institute’s 2022 growing season, they set up an experiment to compare how the same corn hybrid grows with the CryF1 trait vs. the Vip3A trait. The results showed that the CryF1 crop was 50% infected, whereas the Vip3A crop was less than 5% infected with WBCs.

Crop yield was Wilder’s biggest concern, and he saw “a trend for lower yield in the infected [CryF1] corn.”

The “silage made with worm-infected [CryF1] corn had [significantly] higher protein” content, a higher yeast count and were determined to be less palatable, according to Wilder. The “non-infected [Vip3A] corn did have a bit higher starch on average” – almost 3%.

When looking at aerobic stability, Wilder was “a little bit surprised” to see both the CryF1 and Vip3A corn silage heated up, “but the silage that had the worm damage [CryF1] stayed hotter for longer.”

This 2022 experiment supported that a WBC infestation does decrease silage yield and quality. It’s important to note that WBCs are moths in their adult form. They overwinter by burying themselves in the soil and will fly around in July and August to lay eggs on plants and restart the cycle.

Wilder mentioned the pest applies “consistent pest pressure” and that “a lot of people have it and they don’t even know it.” Infestations should be treated and managed based on the pest pressure in your region. Make sure to do more research before dealing with WBCs in your field.

by Kelsi Devolve