2022 Iowa Moth Trapping Network Update: Week 6

Content Author: Ashley Dean

Moth flights into Iowa continued to increase last week. In total, our cooperators captured 118 true armyworm (TAW) moths and 183 black cutworm (BCW) moths during Week 6 (May 1 to May 7).

Week 6 report

Moths of each species were captured almost every day last week. Of the 118 TAW moths, over half were captured on May 5 and May 6. Similarly for BCW, 86 of the 183 BCW moths were captured from May 5 through May 7. Figures 1 and 2 show the Week 6 trap reports for true armyworm and black cutworm, respectively.

A few significant flights of BCW occurred during Week 6. Significant flights occurred in Mahaska (southeast) and Taylor (southwest) counties on May 4, Benton County (east-central) on May 5, and Washington County (southeast) on May 6. In addition to these, we had a few potentially significant flights in Hamilton County (central) on May 2 and Polk County (central) on May 5. I marked them as significant flights on the map because I will use them when predicting cutting dates but based on the number of days between trap reports it is unclear if they are significant flights or not (hence, potentially significant). Remember that the significant flight threshold is over a two-night period; if traps are not checked over the weekend or for more than a few days, it is a bit harder to tell exactly when those moths arrived.

TAW reports May 1 to May 7 2022
Figure 1. True armyworm moth captures from May 1 to May 7. 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 11, 2022.
BCW reports May 1 to May 7 2022
Figure 2. Black cutworm moth captures from May 1 to May 7. 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 11, 2022.

Follow the links to see reports from Week 1, Week 2, Week 3, Week 4, and Week 5. You can also track moth flights and black cutworm significant flights for Iowa, Illinois, and Wisconsin on https://corn.ipmpipe.org/insects/. Within the next few weeks, we will begin predicting cutting dates for Iowa, which will be posted on the corn IPMpipe website and ICM News.

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. I will predict cutting dates across the state by mid-May and share them on ICM News, so make sure you are subscribed!

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 11, 2022. The information contained within may not be the most current and accurate depending on when it is accessed.