Black cutworm (Agrotis ipsilon) is an occasional pest of corn and soybean in Iowa. This insect cannot overwinter here, so spring storms deliver moths to Iowa each year. Because they are migratory, their occurrence in the state is sporadic, and scouting is essential to determine whether fields require treatment for black cutworm larvae. Trapping for moths is a relatively simple way to understand which regions may be at higher risk and predict when larvae may be active in fields.
Why do we care about black cutworm?
The larvae, which are caterpillars, feed on leaves and stems of plants. Large larvae can completely cut through tender stems, like corn stalks or seedling soybeans, and completely kill plants (Figure 1). Black cutworm larvae are large enough to cut plants when they reach the fourth instar. We can predict when this will occur based on accumulating degree days from the occurrence of a significant flight (biofix). A significant flight is defined as the capture of eight or more moths over a two-night period in a pheromone trap. Larvae reach the fourth instar after 300 GDD (base 50°F) have accumulated from the biofix. For more information on black cutworm identification, injury, and management options, read the black cutworm encyclopedia article.
Moth traps monitor for significant flights
The Iowa Moth Trapping Network enlists the help of volunteers around the state to monitor black cutworm flights annually. In 2026, we have 17 individuals monitoring 22 traps around the state. Because we rely on volunteers, not every region has a trap. Volunteers placed wing-style traps baited with sex pheromones that attract male black cutworm moths in early April (Figure 2) and monitor them every few days for new arrivals.
Trapping update
Between April 1 and April 14, 14 trap sites have reported a total of 100 black cutworm moths captured in traps. Although a lot of moth activity is happening, only two of those sites reported significant flights (Figure 3). Tama and Jackson counties reported more than eight moths in their traps on Monday, April 13 (Figure 4).
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. Actual spring temperatures will change these projections, so stay tuned to weekly updates! Remember that it is recommended to begin scouting well before these predicted dates to find larvae before they cut plants.
| County (Crop Reporting District) | Significant Flight Date (Biofix) | Projected Cutting Date(s) |
|---|---|---|
| Tama (Central) | April 12 | May 18 |
| Jackson (East Central) | April 12 | May 18 |
What about true armyworm?
The Iowa Moth Trapping Network is not reporting true armyworm moth captures in 2026, but we encourage scouting for this pest, especially in fields with cover crops or other actively growing, green tissue this spring that is attractive to egg-laying females as they migrate to Iowa. We have heard a few reports recently of people seeing true armyworm moths flying around at night, so they are likely here and laying eggs. There is no method of predicting their activity in fields, so be diligent about scouting! Learn more about what to look for and which fields are at highest risk for true armyworm in the true armyworm encyclopedia article.
More Information
For more information on black cutworm identification, injury, and management options, read the black cutworm encyclopedia article.
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 April 15, 2026. The information contained within may not be the most current and accurate depending on when it is accessed.
- Extension Specialist II