MADISON — Western bean cutworm was originally a secondary pest in the native western range of the U.S., according to Chris DiFonzo, a field crops entomologist and professor at Michigan State University. However, once it moved into Iowa in 2001, more and more attention was paid to the insect, which can now be found as far east as Prince Edward Island, Canada.
“It’s become a much more important pest,” she told attendees to her session on Western bean cutworm management at the Wisconsin Agribusiness Classic in mid-January.
A Cry1F genetic failure in the Corn Belt in 2016 made things even more challenging in terms of managing Western bean cutworm, as farmers believed the genetics would keep their crops safe from the pest.
The impact of the pest on yield is a concern for growers in the Corn Belt, but in Michigan — and presumably neighboring states — large infestations like the ones found in the Corn Belt are less typical.
“It’ a quality issue for us in the Great Lakes Region,” DiFonzo said.
The Western bean cutworm feeds on the tip of the corn ear, opening up the ear and husk to other insects as well. The females are also experts at picking cornfields in their pre-tassel stage to lay their eggs.
There are steps to manage this pest, including trapping moths to detect flights and scouting both Bt-corn fields and non-Bt-corn fields. The majority of fields should be scouted, regardless of Bt, unlike recommendations given before, DiFonzo said.
To help train employees to spot the egg masses and identify them, she also suggested using Wite-Out to paint faux egg masses on corn leaves to simulate an infestation. She recommended when identifying egg masses to place the sun behind the corn’s upper canopy to see them more easily. DiFonzo also wears a face shield when in the fields to allow for a better focus on scouting.
As for spraying, DiFonzo said that once a farmer has reached the cumulative threshold for Western bean cutworm egg masses, they only have about a week to spray for the pest. She prefers one well-timed spray for Western bean cutworm using ground spraying for better coverage, adding that farmers should take advantage of scouting instead of continuously spraying.
“Western bean cutworm requires you to manage expectations, which are unrealistic,” she said.
Farmers will have to rely on good scouting of their fields and do it more than just once, DiFonzo said, but they also need to realize that nothing will ever protect their fields from Western bean cutworm and control the pest 100 percent.