Final Iowa Moth Trapping Network Update for 2023

June 6, 2023 11:06 AM
Blog Post

The trapping season for true armyworm (TAW) and 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 31 volunteers participate from 26 counties in Iowa. A total of 34 BCW and 34 TAW 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 8 report:

During the final days of the trapping network (May 21 to May 30), our cooperators reported 7 TAW (Figure 1) and 32 BCW (Figure 2) moths statewide. Most of these reports occurred between May 21 and May 23. No additional significant flights of black cutworm occurred during Week 8.

TAW reports May 21 to May 30 2023
Figure 1. True armyworm moth captures from May 21 to May 30. The bold number indicates the total moth count for the week (for counties with multiple sites, only the site with the highest total moth count is reported), while the smaller number in parentheses is a running total of the moth count for that trap location. Data is current as of June 5, 2023.

BCW reports May 21 to May 30 2023
Figure 2. Black cutworm moth captures from May 21 to May 30. The bold number indicates the total moth count for the week (for counties with multiple sites, only the site with the highest total moth count is reported), while the smaller number in parentheses is a running total of the moth count for that trap location. Data is current as of June 5, 2023.

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. Figures 3 and 4 show the total number of true armyworm and black cutworm moths reported, respectively, in each county from April 1 to June 1. In total, our cooperators reported 743 TAW and 775 BCW moths across the state during the trapping season. Even with fewer trap locations this year, our cooperators caught twice as many true armyworm moths in 2023 compared to 2022.

Total TAW reports from April to June
Figure 3. Total true armyworm moth captures during the trapping season (April 1 to June 1). For counties with multiple sites, only the site with the highest total moth count for the season is reported. Data is current as of June 5, 2023.

Total BCW reports from April to June
Figure 4. Total black cutworm moth captures during the trapping season (April 1 to June 1). For counties with multiple sites, only the site with the highest total moth count for the season is reported. Data is current as of June 5, 2023.

Report larvae!

If you see larvae or evidence of feeding by either pest, please email bugtraps@iastate.edu and include species, larva size, plant growth stage, and date observed. This can help us refine our predictions in the future.

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 https://corn.ipmpipe.org/insects/black-cutworm/. Although no new significant flights occurred last week, continue to scout cornfields weekly until V5 to account for any prolonged arrival of BCW larvae into the area. We continue to hear reports of black cutworm feeding from around the state, including feeding on V6 corn that does not result in cutting (Photo 1).

black cutworm Gentry Sorenson
Photo 1. Black cutworm (on the soil to the left of the plant) and feeding injury to V6 corn. Photo by Gentry Sorenson (northwest/north central IA).

No such thresholds exist for TAW, so captures reported here should be used as a guide to begin scouting for TAW larvae in corn. Larvae defoliate leaves throughout the summer, sometimes leaving only stalks and midribs behind. Crops are typically damaged by larvae that move from field borders, grassy weeds in the field, cover crops, or adjacent crops. The University of Minnesota has a good resource for armyworm identification, scouting, and management. We have heard several reports from central and north central Iowa of true armyworm feeding, especially in fields that had a cover crop this spring (Photo 2).

true armyworm Ashley Dean
Photo 2. True armyworm larvae under rye that had been roller-crimped in central Iowa. Photo by Ashley Dean.

Past reports and other information

Follow the links to see the report from Week 1, Week 2, Week 3, Week 4, Week 5, Week 6, or Week 7. You can also track moth flights and black cutworm significant flights for Iowa, Illinois, and Wisconsin at 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:

Author: 

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 ...