For the first time during the 2021 moth trapping season, more total true armyworm moths were reported than black cutworm moths. During Week 8 of the Iowa Moth Trapping Network, our cooperators reported 109 total black cutworm (BCW) and 128 true armyworm (TAW) moths.
Week 8 report:
The TAW moths reported during Week 8 were captured statewide and throughout the entire week, but most TAW moths were reported on May 17 (Figure 1). Reports of BCW were also statewide but sporadic throughout the week (Figure 2). New significant flights of BCW were reported in the following counties:
- Taylor County (SW) – May 17; projected cutting date: June 3
- Benton County (EC) – May 19; projected cutting date: June 5
- Washington County (SE) – May 19; projected cutting date: June 4
Reports that indicated a potentially significant flight took place include the following counties:
- Plymouth county (NW) – May 19; projected cutting date: June 5
- Floyd (NC) – May 20; projected cutting date: June 5
- Tama (C) – May 20; projected cutting date: June 5
What does this mean? You may recall that we predicted cutting dates for black cutworm earlier this month. Those predictions were based on significant flights that occurred during April and are still relevant. Those dates represent a starting point for scouting corn for cutting and larvae. Moths continue to migrate into Iowa and lay eggs. The new significant flights and projected cutting dates may be used as a guideline for scouting. You can also see them on the 3rd map at https://corn.ipmpipe.org/insects/black-cutworm/.
Remember that scouting should confirm that plant damage has occurred, larvae are present in the field, and larvae are still actively cutting plants (< 1 ½ inch long) before a treatment decision is made. Corn is not considered susceptible to cutting once plants reach the V5 growth stage.
These updates are typically a week behind. Stay up-to-date by visiting https://corn.ipmpipe.org/insects/ to see live mapping from Iowa, Wisconsin, and Illinois.
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: