Black cutworm moths do not overwinter in Iowa and must migrate north annually. Traps for black cutworm placed around state capture the moths to help determine if management is needed to control cutworm. After flying into Iowa, the moths lay eggs in fields, the eggs hatch and cutworm larvae are produced. Those cutworms can clip off young corn plants and reduce stands. You should start watching fields for signs of cutworm damage beginning when corn emerges.
Because black cutworm moths are attracted to green vegetation for egg laying, infestations of cutworm larvae usually appear first in weedy areas of fields. Newly hatched larvae feed on weeds, and/or young corn plants if present, leaving small irregular holes in the leaves.
Iowa State University Extension entomologist Erin Hodgson and Adam Sisson, an integrated pest management specialist at ISU, along with Laura Jesse, who manages the plant and insect diagnostic clinic at ISU, offer the following information.
Significant moth captures in traps in early and mid-April this year
This year, the traps Black cutworm moths have been collected in Iowa since the beginning of April. Seeing significant moth captures in early and mid-April is unusual and could indicate a more frequent incidence of vegetative crop injury compared to other years. There have been reports of black cutworm moth trap catches from other states besides Iowa, including Minnesota, Illinois, Indiana, Missouri, and Kentucky. In some places, such as Indiana, peak flights are being reported. A peak flight is a specific number of moths caught in a trap that signals when to begin adding up temperature data to figure out when to scout for larvae.
The Iowa State University Extension and Outreach IPM Program organizes a network of farmers, agronomists, Extension personnel, and others to monitor black cutworm traps around state (see second photo). At least one county in Iowa has reported a peak flight so far this season, while lots of traps are reporting low numbers. Of the 101 traps placed across Iowa, 46 haven't caught a single moth as of April 23.
The sporadic nature of this mobile pest makes scouting essential to determine if management is needed. The IPM Program uses this moth capture data and temperature data to estimate when farmers are most likely to see larvae in their fields. Adult moth trap captures do not necessarily mean there will be economically significant black cutworm infestations in a particular location, however. Field scouting is essential to determine if an economically damaging infestation exists.
Look for a future Iowa State University Integrated Crop Management news article, including a map, for the estimated black cutworm cutting data in Iowa when peak flights are determined.
Adam Sisson is an ISU Extension specialist for the Integrated Pest Management. He can be contacted by email at [email protected] or by calling 515-294-5899. Laura Jesse is an entomologist with ISU Extension Plant and Insect Diagnostic Clinic; contact at [email protected] or by phone 515-294-0581. Erin Hodgson is an assistant professor of entomology with Extension and research responsibilities; contact her at [email protected] or phone 515-294-2847.