The New Year often arrives with some reflection. Unfortunately, not everything in 2024 was a positive reflection, including another season of fall armyworm larvae feeding on bromegrass.
A trapping network instituted across the state in 2023 to monitor fall armyworm moth levels is still getting the bugs worked out (pun intended…) and took another step in 2024 with regular moth number reports. While not intended as a way to predict damage, it does paint an interesting picture of what moth numbers are doing during the growing season.
For example, moths pressure may have been higher earlier in the season than noticed. Traps were monitored weekly starting in mid-July with moths found the first week out. Numbers varied, but one location had moth captures in 17 of 18 weeks it was monitored. The second had months captured in 11 of the 15 weeks it was monitored. Early season trapping may not tell us a great deal (there’s generally ample forage for feeding without a lot of damage), but it is interesting to note there were likely already numbers present in mid-July.Second, individual field scouting is still important. Moth numbers were reflective of when we heard feeding reports, but they lagged slightly. Numbers in the trap in the central part of the District were highest shortly after the first damage reports. It will take more work looking at weather patterns, consistency among traps, etc… before it is an accurate warning network.
One of the difficulties is location by location variability. The peak moth flight in the trap near Holton occurred in early September with numbers 10X higher than any other week during the season. Numbers in the trap near Grantville showed a slight increase during that time, with the largest numbers not occurring until later than expected in mid-November. While never reaching the Holton trap’s levels, numbers had been consistently building for three weeks.
Trapping will continue in 2025 looking at the effects of weather and harvest timing. With luck, we won’t get any data – because there won’t be any moths!
