This last week (April 27 – May 3, 2025) was a another relatively active week for moth activity across the state for both black cutworm and true armyworm moths.
A total of 107 black cutworm (BCW) moths were reported last week. Three reports included significant flights: Story County (April 27), Lucas County (April 28), and Pottawattamie County (April 29).
As a reminder a significant flight of BCW occurs when 8 or more moths are captured over a two-night period; this serves as the “biofix” for degree-day accumulation and indicates an increased risk of black cutworm injury in corn. A degree-day model for black cutworm development predicts that larvae are large enough (4th instar or larger) to cut corn plants once 300-degree days (base 50°F) have accumulated since a significant flight occurred. We will predict cutting dates across the state by the middle part of May, and they will be shared on ICM News, so make sure you are subscribed!
Figure 1 below shows where moth traps are established throughout Iowa and summarizes black cutworm moth trap captures by county.
For true armyworms, 81 total moths were reported over the last week. Figure 2 below shows where the traps are established, and true armyworm moth trap captures by county.
Follow the links to see the first and second moth trapping network updates for 2025. You can also track moth flights, black cutworm significant flights, and projected cutting dates for Iowa, Illinois, and Wisconsin on https://corn.ipmpipe.org/insects/. Please note that we are still working on getting the Iowa data included on this map for 2025.
Surrounding states also monitor and report black cutworm and true armyworm captures. If you live near the state border, it may be beneficial to check these resources periodically. More resources may be available than what is 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 4, 2025. The information contained within may not be the most current and accurate depending on when it is accessed.
- Field Agronomist in EC/SE Iowa