By ANN HINCH
Assistant Editor RENSSELAER, Ind. — Of all the things Jasper County agriculture would like to be known for, “home” to the damaging Western Bean Cutworm is probably not one of them.
“Most of it’s just tip-feeding,” said Bryan Overstreet, Purdue University extension educator for the county.
He said the worm had damaged some corn on farms in Jasper and other northwestern Indiana counties, but it’s not what he would term “critical” or economically significant. Further, he said the worm will pupate soon for the winter, for which it must leave the corn and burrow into the soil.
“You could argue it isn’t a pest in Indiana yet of any consequence,” added Christian Krupke, Purdue University Extension entomologist.
“It’s nowhere near ‘ruling the roost’ in what we call a pest.”
Regular haunts Last year, adult male moths were caught in traps in Indiana, but researchers found no larvae (the worms). Traps are placed on farms here and in Illinois, Missouri and other states that wish to cooperate with efforts of Iowa State University (ISU) entomologists tracking the cutworm’s eastward migration.
Two years ago, moths were found as far east as Ohio, according to Rich Pope, ISU Extension program specialist; they were recently found in northwestern Kentucky, and Pope believes traps may even be set in Maryland soon. Iowa especially has had problems with the cutworm since visible damage to ear corn was first reported in 1999 or 2000.
Native to North America, Pope said the cutworm is believed to have originated in Mexico and Arizona, first found decades ago. Colorado and Nebraska have historically had significant damage, and several years ago the moths began moving toward the eastern Corn Belt.
Each season seems to raise more questions than research can immediately answer. For example, does the cutworm like certain types of corn more than others? Why is infestation sometimes sporadic, rather than annual? Perhaps most puzzling is how long the moths have actually lived east of Nebraska.
“Are we finding them because we haven’t looked for them before?” Pope asked. “Or is it really because they’re expanding east?”
Characteristics This worm gets its name from the fact it was first found feeding on dry beans and legumes (not soybeans), though Krupke said it can show up in tomatoes and peppers as well as corn. It’s easy to mistake the creature for corn earworm if not looking for the differences.
The cutworm, said Pope, can be gray with a faint chevron pattern on its segmented body. Krupke added young larvae are often tan and become a pale brown as they develop. The earworm is covered in small, stiff hairs and can be one of many colors, but generally has an orange head cap.
A sure sign a farmer isn’t experiencing earworm damage is if they find more than one worm on a single ear of corn – earworms are cannibalistic, while cutworms can feed together. Both Krupke and Pope pointed out this is why the cutworm may do more damage than the earworm, and Pope said he’s heard Iowa farmers lament cutworm losses as high as 50-75 bushels an acre in some fields.
Cutworms, like earworms, are only hatched once a year, not long after the adult moths lay eggs in June or July. Krupke said the new larvae will burrow into the husks and begin feeding, which generally lasts a month to six weeks; damage isn’t usually apparent until the last three weeks.
Once stuffed full of corn, the cutworms drop off and burrow into the ground to pupate into adults. Krupke said now is about that time of year, far too late to spray insecticide. In fact, Pope explained, spraying is really only effective between when the eggs hatch and the larvae start burrowing into corn ears, a short period of a week to 10 days.
“Once it’s under the husks, you’ve lost your shot at killing it,” Pope said. “Scouting in corn is not very fun in the heat of July and August, but that’s exactly what we’re asking farmers to do.”
Another way to counter the cutworm is to plant Bt corn genetically engineered to control it. Right now, the only anti-cutworm varieties of which Krupke and Pope are aware are marketed by Pioneer Hi-Bred. Though it’s too late to kill larvae this year, Pope said it’s good to plan ahead. By scouting their fields right now, Midwestern growers can determine if next year’s crop might be at risk. Since cutworms hibernate in the soil of the fields where they’ve munched, there’s a good chance as adults they may lay eggs near there the following season.
Farmers who find telltale signs – such as multiple worms in one ear of corn – should contact their county extension office. In Indiana, they may also contact Krupke at 765-494-4912 or by e-mail at ckrupke@purdue.edu
To learn more about ISU’s cutworm research, visit www.ipm.iastate.edu/ipm/icm/taxonomy/term/586 This farm news was published in the Aug. 29, 2007 issue of Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee. |
