Trapping Update
Between May 18 and May 24, 16 trap sites reported a total of 73 black cutworm moths captured in traps (Figure 1). There was a significant flight reported in Franklin County on May 18 (Figure 2).
Plan to Scout!
Using historical temperature data from the Midwest Regional Climate Center database, Table 1 shows the current projected cutting dates in counties that have had a significant flight.
Some cutting date predictions have already passed, so it is crucial to scout fields as crops emerge, especially in areas with green plants at the time of planting that could harbor cutworms. Plan to scout well in advance of cutting dates that have not occurred yet.
| County (Crop Reporting District) | Significant Flight Date (Biofix) | Projected Cutting Date |
|---|---|---|
| Jackson (East Central) | April 12 | May 9 |
| Tama (Central) | April 12 | May 10 |
| Polk (Central) | April 13 | May 10 |
| Buena Vista (Northwest) | April 22 | May 23 |
| Cerro Gordo (North Central) | April 22 | May 22 |
| Franklin (North Central) | April 22 | May 22 |
| Marshall (Central) | April 24 | May 21 |
| Tama (Central) | April 24 | May 21 |
| Washington (Southeast) | April 26 | May 21 |
| Jackson (East Central) | April 28 | May 24 |
| Tama (Central) | May 17 | June 5 |
| Plymouth (Northwest) | May 17 | June 6 |
| Franklin (North Central) | May 18 | June 8 |
These dates may differ from what was reported in the ICM News article about predicted cutting dates for a few reasons: I update the blog weekly using actual temperature data, and cutting dates for regions without traps or significant flights are our best estimates based on available data.
Caterpillars Found
Over the past week or so as corn has grown rapidly and folks are out checking stand, we have heard several reports of cutworm injury from all around the state. There seems to be a mix of black and dingy cutworms in some fields. Here are some resources to learn more about cutworms:
Black cutworm encyclopedia article
ICM Blog post about cutworms in forages
In addition to cutworms, we have also heard a few isolated reports of true armyworm feeding in corn. Armyworms do not tend to cut corn plants like cutworms do, but young plants can be completely defoliated when large populations are present. Keep an eye out for any caterpillars, and watch for leaf feeding or cut, wilted, or dead plants. Many species are nocturnal and may be difficult to find during the day, but looking under residue or digging through the soil may reveal larvae.
More Information
For more information on black cutworm identification, injury, and management options, read the black cutworm encyclopedia article. You can find previous weekly reports on the ICM Blog.
Surrounding states also monitor and report black cutworm captures, as well as other moth species. If you live near the state border, it may be beneficial to check these resources periodically. More resources may be available than those listed here:
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Integrated Crop Management News, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on May 28, 2026. The information contained within may not be the most current and accurate depending on when it is accessed.
- Extension Specialist II