BCW 2024 Issue 06

Report #6 May 11-17, 2024
For more information: https://z.umn.edu/bcw-reporting 
May 21, 2024

Greetings:

A map of minnesota with different colored areas showing BCW moth captures My 11-17,2024 and second image showing captures for 2024 traping season ending May 17

It was a relatively calm week for migrating black cutworm moths (Figure 1, Table 1). The exception was a May 14 significant capture for the Polk County trap. Large moth captures this early in the season do not often occur this far north. Similarly, because of spring weather patterns, captures are often higher in states to our south and east than in southern MN.  Weather systems that allow black cutworm moths further north in Minnesota tend to occur more often later in the spring. 

Figure 2 shows the season’s highest two-night black cutworm moth captures for each county. In spite of our Maginot Line-like trap network, keep in mind these maps are not absolutes.  Degree day predictions to help time scouting for 2024 moth captures can be found in Table 2 The larvae from the earliest moth flights will have molted two times and be at the 3rd larval stage (instar). The earliest may be 4th instar and be able to cut small corn now. Cutting by larvae from later flights is more likely the last week of May. 

I just received a report of cutworm feeding in sugarbeets in a Renville County field. I do not know which species of cutworm was involved or the extent of stand damage.  As mentioned in earlier issues, the Renville, Brown, and Nicollet County traps have been very active this spring although black cutworm can appear anywhere in southern MN, although black cutworm can appear anywhere in southern MN. 

You can find additional scouting information in black cutworm on corn.

Table 1. Positive captures in pheromone traps reported May 11-17, 2024
Table 2. Projections based on historical average temperatures.

True armyworm (TAW)
Other than the mid-May captures in LeSueur and Waseca Counties, armyworm moth captures in southern MN pheromone traps have captured few moths. We do not have as extensive a trapping network for armyworm moths as for black cutworms. However, Dave Grafstrom is running several pheromone traps in grass seed production fields in Roseau County. They captured large numbers (17-28/trap) of armyworm moths over the weekend.  These moths appear to have been aided by a system that went through the NW corner of Minnesota. 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.

This project is supported, in part, by the farm families of Minnesota and their corn check-off investment.

Until next week, 
Bruce Potter