Even though the weather has been variable this past week, one thing is certain: black cutworm is moving through Iowa. During week 2 of the Iowa Moth Trapping Network (April 4 to April 10), our cooperators reported 122 total black cutworm (BCW) and 21 true armyworm (TAW) moths. Windy conditions last week likely helped move so many moths into the state. Both species take advantage of powerful low-level jet streams at night to move long distances from their overwintering sites in the south. If you are interested in seeing real-time maps of black cutworm and true armyworm captures in Iowa and other participating states, use the links provided or select the species at https://corn.ipmpipe.org/insects/.
Week 2 report:
The 21 TAW moths were captured across the state and pretty evenly throughout the week (Figure 1). However, nearly half of the 122 BCW moths caught last week were reported on Friday, April 9. All BCW moths were caught from April 6-9. Significant flights of black cutworm occurred in Benton (east-central), Mahaska (southeast), Washington (southeast), Taylor (southwest), and Monona (west-central) counties. Another potentially significant flight occurred in O’Brien (northwest) county (Figure 2).
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. 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!
Follow this link to see the report from Week 1.
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: