Windy conditions last week brought our first large flights of black cutworm (BCW) and true armyworm (TAW) moths to Iowa. During Week 3 (April 10 to April 16), our cooperators reported a total of 49 BCW and 20 TAW moths throughout the state.
Week 3 report:
More than half of the moths captured last week were reported on April 13 following the first day with winds exceeding 10 mph. One significant flight of black cutworm occurred in Taylor County (southwest). Figures 1 and 2 show the Week 3 trap reports for true armyworm and black cutworm, respectively.
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!
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: