Agriculture Online
05-22-07
Black cutworms found in Iowa; focus turns to scouting
Jeff Caldwell
Agriculture Online News and Features Editor
Black cutworms that were causing economic damage to corn fields in the central
and eastern Corn Belt last week are heading west.
Agronomists with Pioneer Hi-Bred International, Inc., confirmed that heavierthan-normal cutworm moth flights this spring have materialized into larvae
populations in the southeastern part of Iowa, where agronomists have observed
"scattered cuttings." In 2006, Jasper, Poweshiek and Keokuk counties in Iowa
saw heavy infestations, according to Pioneer.
Last week, Pioneer and University of Illinois officials confirmed black cutworm
cutting underway in Illinois. There, agronomists said cutworm moths likely rode
stronger-than-normal southerly wind currents earlier on in the spring.
Field scouting for the pest is now the top priority for black cutworms in the
affected areas. By carefully scouting, University of Illinois Extension entomologist
Kevin Steffey says growers can get ahead of serious cutting damage -especially in younger corn plants -- by watching for leaf-feeding.
"Be prepared, especially in areas where corn has yet to be planted or has just
gone into the ground," Steffey says. "Populations of black cutworms will only
increase as moths continue to fly...but even in areas with corn emerging, be sure
to check fields for black cutworms and symptoms of their feeding injury.
"Leaf-feeding injury is not economic, but it is a precursor to stand-reducing
cutting damage."
In scouting, however, Steffey says it's important to distinguish between black
cutworms and other species that cause little or no damage, like the dingy
cutworm. According to Iowa State University entomologist Marlin Rice, there
are a few characteristics of dingy and black cutworms that should set them apart
in scouting fields.
"Black and dingy cutworms are separated by two distinctive features: Skin texture
and relative tubercle (wart) diameter. Blacks have grainy skin like sandpaper,
whereas dingys have smooth skin. You will need a good hand lens to see this
feature," Rice recently wrote. "Identification also is based on the size of the four
tubercles along the top center of each body segment. On the dingy cutworm,
these tubercles are about the same diameter. On the black cutworm, the inside
pair of tubercles (or the pair closest to the head) is about half the diameter of the
outside pair."