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.
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:
- University of Minnesota
- University of Missouri
- University of Illinois
- University of Nebraska-Lincoln
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!
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 ...