Keep An Eye Out For Slugs and Bugs

Growing season has already taught a few cutworm lessons.

Published on: Jun 7, 2011

On May 12, this web site issued a warning that "squadrons" of black cutworm moths were migrating north toward the Mid-Atlantic. Some of them landed in a highly visible soybean field along side a well traveled highway south of Shippensburg, Pa., and dropped their bombs – eggs turning into voraciously eating cutworms. It happened to be in Gro-Land Farms' corn trial plot.

Garst District Sales Manager Dervin Druist called it "the perfect bug storm". A week ago Friday, the field had been scouted with only a few slugs reported. Between that Friday and the following Monday, slug and black cutworm populations exploded, and revealed substantial differences in black cutworm suppression of Bt hybrids.

SHOW-AND-TELL: Agronomists and interested farmers checked out the hybrid plot differences in cutwork suppression. Jay Grove is in the middle.
SHOW-AND-TELL: Agronomists and interested farmers checked out the hybrid plot differences in cutwork suppression. Jay Grove is in the middle.

Gro-Land Farms wasn't the first or last to discover such differences. "Many growers across the Corn Belt are finding out what black cutworm "suppression" really means," acknowledges Penn State Extension Entomolgist John Tooker. "And, they don't appear pleased."

Jay Grove took it as well as could be expected, considering his corn plot had been struck by slugs, black cutworms and quite likely flea beetles, with lightning force. The differences between Pioneer's Herculex Extra, DeKalb's VT Triple Pro and Garst Viptera hybrids were clear down to the row with cutworms doing most of the damage.

CONVERSATION STARTER: Grove had been planting the Viptera test strip, got involved in an in-cab conversation. "I started back down the field and forgot to switch hybrids." Where he switched to a BT hybrid without strong cutworm suppression, few plants survived.
CONVERSATION STARTER: Grove had been planting the Viptera test strip, got involved in an in-cab conversation. "I started back down the field and forgot to switch hybrids." Where he switched to a BT hybrid without strong cutworm suppression, few plants survived.

The incident occurred in a no-till field where soybeans were grown last year. It was an unlikely field for experiencing cutworm damage, according to Grove. The Viptera corn experiences no cutworm damage. The VT Triple Pro experiences substantial damage while the Herculex Extra corn suffered the most.

The plots were not intended for black cutworm comparisons. As Grove rightly points out: "Cutworm risks are impossible to predict much more than a week before they strike. We had corn with corn borer resistance on the outside of the field, and the cutworms didn't seem to like it either."

Lesson learned?

"With seed costs of $250 to $300 a bag and corn worth more than $6 a bushel, we really can't afford to lose a population," says Grove. "The risk is so much higher today. Next season, we expect we'll be spraying or at least be ready to do so much quicker."

The big question, contends Grove, isn't whether cutworm risks are high enough to justify the extra protection designed into a hybrid. It's whether risks of other corn insects are high enough.