2017 U of MN Cooperative Black Cutworm Trapping Network Issue 6

Report #6 Week of April 29 - May 5, 2017

This report is also available in a print-friendly pdf format: 2017 Black Cutworm Network Issue 6

Black cutworm moth captures throughout participating counties in southern MinnesotaOnce again, locations scattered through the trapping area reported captures (Figure 1). So far, the trap captures in Minnesota this year remain smaller than those reported from states to the east.

While there is some risk of damage from black cutworm in 2017, at this point, it appears to be fairly low and not widespread.

However, a trap in Redwood County picked up a significant flight on April 29-30. This is the second significant flight into this area. Rock and Steele Counties also picked up single moths at this time.

Scattered counties reported captures of widespread but low level flight of 1-4 moths; indicating a small influx of moths, May 3-4. When assessing risk from black cutworms, the location of traps with low or no captures is as important to note as those with large captures.

Other locations with captures are listed below: 

Trap & Co. #/2 Nights Date(s)
Brown  4 5/1 - 5/5
Brown  2 5/3
Dakota 1 5/1
Martin 1 5/3
Meeker 2 5/5
Nicollet 1 5/4
Nicollet 4 5/4
Nobles 1 5/4
Redwood 9 4/29 - 4/30
Rock 1 4/30
Sibley 2 5/5 & 1 on 5/3
Steele 1 4/30
Swift 2 5/4 - 5/5

There have been two significant flights April 15 and April 29. Both have been into the Brown and Redwood county area. Larvae from the first light should be large enough to cut small corn near the end of the month and emerging sugarbeets perhaps a bit earlier. Much depends on soil temperatures and how quickly corn develops. Where fields were worked before these dates, risk of black cutworm damage is lowered.

As of now, it still looks the highest probability for any threatening black cutworm populations is in the western Brown, eastern Redwood Co. area. Other areas cannot be assumed risk free because of the very localized nature of some of these immigrations. Don’t ignore black and other cutworm species when scouting.

Below are dates and locations of significant flights and estimates of cutworm stages and for these flights, when cutting is projected to start with 4th instar larvae and end when the larvae pupate.

2017 Black Cutworm Cutting Projections
Biofix Flight Date Counties Accumulated Degree-Days Estimated Stage Projected Cutting Start Projected Pupation
April 15 Brown 151 2nd instar May 29 June 13
April 29 Redwood 94 1st instar June 2 June 22

The U2U corn growing degree-day calculator http://mrcc.sws.uiuc.edu/U2U/ at the Midwest Regional Climate Center is very helpful in projecting cutworm (and corn) development.

Corn and soybean planting is in full swing and the number of fields at risk from future flights are decreasing quickly. In many fields, there has been a considerable amount of early season weed growth before tillage.

Until next week,

Bruce Potter and Travis Vollmer