Final Iowa Moth Trapping Network Update for 2024

June 5, 2024 2:36 PM
Blog Post

The trapping season for black cutworm (BCW) has come to an end. We appreciate our cooperators for tirelessly checking traps the last two months and reporting their captures so we can provide the most accurate scouting information for these pests. To recap, we had 25 volunteers participate from 24 counties in Iowa. A total of 29 BCW traps were placed and monitored during April and May. Because of these efforts, we were able to provide weekly updates of moth activity and predict cutting dates for BCW in Iowa.

Week 9 report:

During the final days of the trapping network (May 26 to June 1), our cooperators reported 30 BCW (Figure 1) moths statewide. One significant flight occurred in Benton County on May 27.

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 May 26 to June 1 2024
Figure 1. Black cutworm moth captures from May 26 to June 1. 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 June 5, 2024.

Maximum 2-night count of BCW May 26 to June 1 2024
Figure 2. Maximum two-night moth captures in each county during Week 9 (May 26 to June 1). Increasingly intense colors indicate more moths were captured over a two-night period during the week.

Final numbers:

Although more total moths in an area does not necessarily mean you can expect more damage to occur, knowing where moths were captured can give an idea of where to expect activity. Figure 3 shows the total number of black cutworm moths reported in each county from April 1 to June 1. Most counties had one trap site, but Benton, Floyd, Hancock, and Linn counties all had two trap sites, so the total count is averaged for those counties. In total, our cooperators reported 852 BCW moths across the state during the trapping season, which surpasses the total number captured in 2023.

Total BCW moths in 2024
Figure 3. Total black cutworm moth captures during the trapping season (April 1 to June 1 2024). For counties with multiple sites, the total reported is an average across the sites, and the number of trap sites in each county is shown in parentheses in the lower left corner. Data is current as of June 5, 2024.

Report larvae!

You may recall that we predicted cutting dates for BCW in early May and that updated cutting dates were included in weekly updates and on Continue to scout cornfields weekly until V5 to account for any prolonged arrival of BCW larvae into the area. We continue to hear reports around the state of black cutworm feeding. While looking for BCW, also keep an eye out for true armyworm. Although we did not trap for true armyworm this season, they may be present in fields and are attracted to similar fields as black cutworm.

If you see larvae or evidence of feeding by black cutworm or true armyworm, please email and include species, larval size, and date observed. This can help us refine our predictions in the future.

Past reports and other information

Follow the links to see reports from Week 1, Week 2, Week 3, Week 4, Week 5, Week 6, Week 7, and Week 8. You can also track moth flights, black cutworm significant flights, and projected cutting dates for Iowa, Illinois, and Wisconsin on

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:


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 ...