Report #7 May 18-24, 2024
For more information: https://z.umn.edu/bcw-reporting
May 28, 2024
Greetings:
Spring tillage and planting progress had most black cutworm traps shut down last week. Those that were running did not detect any significant moth flights and the season long map of maximum captures was not changed (Figure 1).
Degree day predictions to help time scouting for 2024 moth captures can be found in Table 2. Many larvae are now large enough to cut small corn with some of the larvae from the earliest moth flights may be already at the 5th larval stage (instar). The degree days models seem to be tracking well in eastern Brown County. For example, last Saturday, I was pulling the horseweed contributed by neighbors’ yards last fall. I found late 4th instar larvae where black cutworm moths had taken advantage of the early spring growth.
In spite of the active moth traps this spring, I have not heard of any more cutworm issues. Maybe we have talked them to death. Black cutworm moths tend to lay eggs in low-laying weedy areas standing water may have drowned a few larvae.
Many early planted fields will soon be 5 leaf too large for even late instar larvae to cut.
On the other hand, keep in mind that the last larval instars consume most of the vegetation. Although unable to cut large corn, late instar larvae sometime kill 5 leaf corn by tunnelling into the growing point.
You can find additional information on cutworm ID and economic thresholds in black cutworm on corn.
True armyworm (TAW)
Roseau Count continues to capture large numbers of moths. While some moths have been captured in many other trap locations, numbers have remained low with the possible exception of a couple SC MN traps. Historically, most armyworm problems occur in late June and early July so don’t ignore high risk fields when scouting.
This is shaping up to be one of the cool, wet springs that armyworms often do well in. Remember to keep armyworms in your grass seed, corn and small grain scouting this year. For more information on armyworms see: https://extension.umn.edu/corn-pest-management/armyworm.
Many thanks to 2024 cooperators (2022). You did a great job this spring and provided a perspective on this season’s black cutworm and armyworm risks. Some of you have been helping with this project for a long time. A special thanks to Gretchen Thillen, UMN Southwest Research and Outreach Center for help with getting the newsletters for the web.
This project is supported, in part, by the farm families of Minnesota and their corn check-off investment.
Bruce Potter
University of Minnesota Extension IPM Specialist
University of Minnesota SW Research and Outreach Center
23669 130th Street
Lamberton, MN 56152
[email protected]
Cell: (507) 276-1184