2024 Iowa Moth Trapping Network Update: Week 2

April 17, 2024 1:49 PM
Blog Post

Moth counts ramped up dramatically during Week 2 of the moth trapping network (April 7 to April 13), although we often get large flights with spring storm systems in April. Despite the low captures reported during the first official week, 70 total black cutworm (BCW) moths were reported last week. Most of those captures were reported on April 8 (41 moths), and 16 additional moths were reported on April 11. Two reports included significant flights: Floyd County (April 8) and Muscatine County (April 11).

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!

Figure 1 shows where moth traps are established throughout Iowa and black cutworm trap captures by county. Figure 2 shows the maximum 2-night capture in each county. This is an important distinction because although total moth counts tell us a bit about moth activity in the region, we determine whether a significant flight has occurred based on total captures over two nights. The red coloration on both maps indicate significant flights occurred, but Figure 2 gives a better sense of where large flights occurred even if they were not significant.

BCW Counts April 7 to April 13
Figure 1. Black cutworm moth captures from April 7 to April 13. 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; highlighted counties without numbers indicate that traps are placed but no reports have been received). The number in parenthesis represents the season-long total black cutworm captures in that county. Data is current as of April 17, 2024.

Maximum 2-night count of BCW April 7 to April 13
Figure 2. Maximum two-night moth captures in each county during Week 2 (April 7 to April 13). Increasingly intense colors indicate more moths were captured over a two-night period during the week.

Follow the link to see the report from Week 1. 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 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:


Ashley Dean Agriculture and Natural Resources Extension Specialist II

Ashley is an education extension specialist for field crop entomology at Iowa State University. She 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 ...