As the western bean cutworm (WBC) has continued to spread across the U.S., managing the pest has become increasingly difficult.

The insect has moved from its native home in the southwestern U.S. to Iowa, Michigan and Ohio, with more recent issues emerging as far east as Nova Scotia. Their rapid spread is aided by their increasing resistance to Bt hybrids with the Cry1F protein. Also, unlike corn earworm, WBC larvae are not cannibalistic, so you will often find several larvae in each ear and the high populations can cause heavy damage. 

The tell-tale sign of damage to corn caused by WBC is gouging and sometimes they’ll strip along the top of the kernels and make a white scraping kind of damage.

“Often it’s not actually the amount of corn that they’re eating that makes them a problem or pest. This opens up the corn to mold,” says Ohio State University Extension entomologist Kelley Tilmon, who shared her thoughts on the best way to combat these cutworms and protect no-till corn yields.

Timing Matters

It’s important for growers to understand WBC life stages because this gives them a better idea of when and how to combat it. This species of insect has one generation per year, with adults emerging in late June or early July.

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“It’s best to combat them before the larvae enter the ear of corn because once there, they’re protected from the treatment product.” — Kelley Tilmon

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Eggs, smaller than the lettering on a penny, are laid in…