Although no intense flights (nine or more moths caught over a two-day period) of black cutworm moths have been reported, captures of this species have been common in several Illinois counties and states, said a University of Illinois Extension entomologist.
Mike Gray said that impressive flights of black cutworm and armyworm moths have been reported by Doug Johnson an Extension Entomologist at the University of Kentucky. Entomologists at Purdue University also have received reports that black cutworm moth captures are now common in many areas of Indiana.
He added that Kelly Estes, agricultural pest survey coordinator with the Illinois Natural History Survey, has established a network of trapping cooperators across Illinois. Over the past two weeks, captures have been reported in the following Illinois counties: Champaign, Fayette, Logan, Lee, Macon, Macoupin, and Madison.
"This distribution of captures suggests that black cutworm moth flights have likely taken place throughout Illinois and growers are encouraged to remain vigilant for early signs of leaf feeding when corn seedlings begin to emerge," Gray said. "Today (April 21) strong winds from the south are undoubtedly bringing many black cutworm moths into Illinois, and weedy fields will be prime targets for egg laying by this species."
Gray provided some key life cycle and management facts concerning black cutworms.
- Black cutworm moths are strong migratory insects with northward flights commonly observed from the Gulf States into the Midwest from March through May.
- Moths are attracted to fields heavily infested with weeds such as chickweed, shepherd's purse, peppergrass, and yellow rocket.
- Late tillage and planting tends to increase the susceptibility of fields to black cutworm infestations.
- Cutting of corn plants begins when larvae reach the 4th instar, with a single cutworm cutting an average of three to four plants during its larval development.
- Cutting tends to occur most often during nights or on dark overcast days.
- Fields at greatest risk to cutting and economic damage are in the 1-to-4 leaf stage of plant development.
- An early warning sign of potential economic damage includes small pinhole feeding injury in leaves (caused by the first three instars).
- A nominal threshold of 3 percent cutting of plants has traditionally been used as a point at which growers should consider a rescue treatment.
- Not all Bt hybrids offer adequate protection against black cutworm damage. Growers should consult the Handy Bt trait table prepared by Dr. Chris DiFonzo at Michigan State University to determine the level of protection provided by their chosen Bt hybrid.
"As the season progresses, if you learn of significant black cutworm infestations, please let me know and I will share this information with the readers of the Bulletin," Gray added.