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2022 Iowa Moth Trapping Network Update: Week 8

May 25, 2022
Content Author: Ashley Dean

Last week, moth flights into Iowa continued to decrease compared to previous weeks. In total, our cooperators captured 38 true armyworm (TAW) moths and 65 black cutworm (BCW) moths during Week 8 (May 15 to May 21).

Week 8 report:

Nearly all TAW moths were reported on either May 15 (15 TAW moths) or May 18 (14 TAW moths). The BCW captures were more spread out throughout the week. Two additional significant flights of BCW occurred during Week 8: Taylor County (southwest) on May 15 and Hamilton County (central) on May 20. Based on these significant flights, degree day accumulation, and historical weather data, we project that cutting could occur on June 4 in southwest Iowa and June 9 in central Iowa. Figures 1 and 2 show the Week 8 trap reports for true armyworm and black cutworm, respectively.

TAW reports May 15 to May 21
Figure 1. True armyworm moth captures from May 15 to May 21. The bold number indicates the total moth count for the week (for counties with multiple sites, only the site with the highest weekly moth count is reported), while the smaller number in parentheses is a running total of the moth count for the season; highlighted counties without numbers indicate that traps are placed but no reports have been received. Data is current as of May 25, 2022.
BCW reports May 15 to May 21
Figure 2. Black cutworm moth captures from May 15 to May 21. The bold number indicates the total moth count for the week (for counties with multiple sites, only the site with the highest weekly moth count is reported), while the smaller number in parentheses is a running total of the moth count for the season; highlighted counties without numbers indicate that traps are placed but no reports have been received. Data is current as of May 25, 2022.

Follow the links to see reports from Week 1, Week 2, Week 3, Week 4, Week 5, Week 6, and Week 7. See our initial estimation of cutting dates across Iowa. 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/.

Surrounding states also monitor and report BCW and TAW 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:

What is a significant flight? 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. Cutting dates have been predicted for Iowa: https://crops.extension.iastate.edu/cropnews/2022/05/begin-scouting-black-cutworm-corn

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 25, 2022. The information contained within may not be the most current and accurate depending on when it is accessed.

Authored by
Ashley Dean
Ashley Dean
  • Extension Education Specialist, Entomology
Ashley is an extension specialist for field crop entomology at Iowa State University. Ashley coordinates the Iowa Moth Trapping Network, the Regional Corn Rootworm Monitoring Network, and the Iowa Pest Alert Network. She also develops educational resources for field crop pests in Iowa and aids in the research efforts of the Soybean Research Laboratory.

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