Last week, moth flights into Iowa continued to decrease compared to previous weeks. In total, our cooperators captured 38 true armyworm (TAW) moths and 65 black cutworm (BCW) moths during Week 8 (May 15 to May 21).
Week 8 report:
Nearly all TAW moths were reported on either May 15 (15 TAW moths) or May 18 (14 TAW moths). The BCW captures were more spread out throughout the week. Two additional significant flights of BCW occurred during Week 8: Taylor County (southwest) on May 15 and Hamilton County (central) on May 20. Based on these significant flights, degree day accumulation, and historical weather data, we project that cutting could occur on June 4 in southwest Iowa and June 9 in central Iowa. Figures 1 and 2 show the Week 8 trap reports for true armyworm and black cutworm, respectively.
Follow the links to see reports from Week 1, Week 2, Week 3, Week 4, Week 5, Week 6, and Week 7. See our initial estimation of cutting dates across Iowa here. 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 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. Cutting dates have been predicted for Iowa: https://crops.extension.iastate.edu/cropnews/2022/05/begin-scouting-black-cutworm-corn