By SHELLY STRAUTZ-SPRINGBORN
Michigan Correspondent EAST LANSING, Mich. — Monitoring efforts are under way in Michigan for detection of western bean cutworm (WBC), a severe pest in corn and dry beans that affects crop yield and quality.
Chris DiFonzo, Michigan State University field crops entomologist, said the pest has already been detected in the state this year. To help growers stay abreast of where WBC has been found, she has set up a trapping network throughout the state to capture the moths. She has also created a map that shows where traps are located.
As the growing season progresses, the map will provide infestation counts for each of the traps; visit her site at www.MSUent.com to view the map.
“By monitoring the trapping network data, farmers will know if there’s flight in their area,” DiFonzo said.
Scouting is key to early detection of the pest. Information gathered through the trapping network will be useful to growers to help them determine when to begin scouting their fields.
“Infestation is usually really spotty,” DiFonzo said. “What we find is that one field will need spraying, but another one just down the road won’t. We had infestation last year all across the state.”
During the 2007 growing season, the northwestern quadrant of the state from Oceana County to Montcalm County and north was infested.
Historically, WBC was a pest in the western Corn Belt. It has steadily spread from west to east, and has moved rapidly in the last 10 years.
Unlike other cutworms, WBC is a late-season pest. It feeds primarily on corn ears, chewing and scarring kernels and predisposing the ear to fungal and mold infections. One generation of WBC occurs each year. Moth emergence usually begins in early July.
DiFonzo said she expects to see increased activity during the next few weeks, and researchers are working to monitor the situation throughout the state.
“We’ve had a few moths caught,” she said. “We will start to see egg masses in mid-July.”
DiFonzo said detection is more difficult in dry beans than in corn.
“In corn, you can see them pretty easily. They are right at eye level,” she said. “In dry beans you basically have to crawl around on the ground to find them.”
After mating, females lay eggs on available host plants such as field corn, sweet corn, popcorn or dry edible beans. Typically, the pest is attracted to fields in which corn is tasseling or near tasseling, and fields that have hybrids with upright leaf characteristics.
After hatching, larvae feed on host plants for about 31 days. After a larva finishes feeding and completes development, it drops to the ground and burrows into the soil, where it overwinters.
During years with severe infestations, multiple larvae per ear may be common. Under severe feeding pressure, 50-60 percent of an ear’s kernels may be damaged.
In dry edible beans, eggs are laid in areas of dense bean foliage on the lower surface of leaves. Dry beans are particularly attractive to WBC if neighboring corn fields have already tasseled. Larvae chew holes in pod walls and developing seeds. Most feeding occurs on cloudy days or at night.
If WBC development is not complete, as beans are pulled larvae may congregate under the windrow, feeding on pods and seeds until harvest.
In corn, DiFonzo said clearing up some corn borer infestations by planting Bt corn may have made corn more vulnerable to WBC. “What we see is that some types of Bt corn control this pest and some do not,” she said. “The type that does is Herculex. It may not be 100 percent control, but it is probably as effective as if you were spraying for corn borer.”
DiFonzo said infestation can be managed with insecticides, “but the timing has to be right.” Plus, she said spraying can be more difficult because infestation occurs late in the season, when corn is taller.
“Farmers have to have the right equipment, which may be a challenge,” she said. |
