The 2025 moth trapping season is underway for black cutworm (BCW) and true armyworm (TAW). This year our trapping network includes sites monitored by the extension field agronomists and several of the ISU Research Farms. Monitoring for BCW has been a long-standing project in Iowa, and more recently TAW has been included.
Both of these pests are migratory, making it challenging to predict if, where, and when populations may arrive from one year to the next. We use a wing-style trap baited with a pheromone lure specific for each species. Female moths release pheromones to attract males for mating, and a synthetic version of the pheromones are used for the lures in our traps. Unsuspecting males fly into the trap and are caught in the sticky substance at the bottom.
This trapping network allows us to refine pest movement into the state. Specifically, with BCW, we use the data collected with the trapping network to estimate scouting and treatment windows for farmers based on significant flights. A significant flight of BCW occurs when 8 or more moths are captured in a pheromone trap over two nights. While there is not a similar threshold for TAW, monitoring still allows us to inform farmers in the area and support scouting activities. Since these pests are erratic, the best way to know if BCW or TAW are causing injury to the crop is to scout your fields.
Moth Count Update
Traps were placed either the week of April 7 or the first part of the week of April 14. This was a little later than we typically try to have them set. Consequently, it’s possible there was some moth activity in the state prior to the traps being placed.
The first positive record of moth activity in Iowa this year occurred on April 13 in Hamiliton County, where 1 BCW moth was reported. The first TAW moth was detected on April 17 in Story County.
Several positive detections of BCW and TAW occurred other sites, including a significant flight of BCW being recorded in Story County on April 16. A total of 22 BCW moths and 5 TAW moths were reported across the state since the traps were placed. Figure 1 and 2 show a summary of the BCW and TAW moth counts reported since traps were placed in early April.
You can track black cutworm captures, significant flights, and projected cutting dates for Iowa, Illinois, and Wisconsin at https://corn.ipmpipe.org/insects/. Note that the Iowa data will be added to this site soon.
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:
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- Field Agronomist in EC/SE Iowa