2017 U of MN Cooperative Black Cutworm Trapping Network Issue 4

Report #4 Week of April 15-21, 2017

This report is also available in a print-friendly pdf format: 2017 Black Cutworm Network Issue 4

Black cutworm moth captures in southern MN from April 15-21, 2017

Figure 1. Maximum black cutworm moth captures by county. April 15-21, 2017.

More moth activity last week, April 15-21. Locations scattered through the trapping area reported captures, minor for the most part (Figure 1).

The Brown County trap mentioned last week had more activity. The cooperator dropped off a trap bottom over the weekend. The photo he sent on the 15th indeed showed black cutworm moths. In addition to the 8 moths captured on the 15th, his trap captured 10 more during the week (Figure 2). A Redwood County trap had 6 moths on the 17th, and these could have arrived on the same weather system as the Brown County moths. Just as important as the captures in Brown and Redwood are the no and low captures in surrounding areas.

Figure 3 shows a NOAA precipitation map for April 15th. I highlighted the backside of the system that likely brought these moths in. This relatively small system and the localized area with significant trap captures should help illustrate why numerous traps are needed to detect specific insect migrations.

Black cutworm trap with moth captures from Brown County

Figure 2. These male black cutworm moths fell for the old "fake pheromone" trick. Black cutworm moth migrations are often very spotty and related to thunderstorm activity.

The several weather systems brought scattered precipitation and black cutworm moths through the week. Rice County had a single night capture of 4 moths on the 18th. Other locations with captures are listed below:

  • Big Stone - 1 on the 15th
  • Brown - 8 on the 15th and 10 more the rest of the week
  • Brown - 2 on the 17th and 2 on the 18th
  • Dakota - 2 on the 18th
  • Dodge - 2 on the 20th
  • Goodhue - 1 on the 21st
  • Lac Qui Parle - 1 on the 19th
  • Lyon - 2 on the 21st
  • Murray - 1 on the 15th
  • Nicollet - 2 on the 18th
  • Nicollet - 2 on the 17th
  • Olmsted - 1 on the 15th and 1 on the 16th
  • Olmsted - 1 on the 19th
  • Redwood - 6 on the 17th
  • Redwood - 1 on the 21st
  • Rice - 4 on the 18th
  • Rock - 2 on the 16th and 1 on the 18th
  • Steele - 1 on the 18th
  • Steele - 2 on the 20th
  • Swift - 2 on the 17th
  • Wabasha - 2 on the 16th
  • Waseca - 1 on the 18th
  • Waseca - 2 on the 21st

In spite of the slow spring in many areas, corn planting and spring tillage of soybean residue has occurred. Those fields where 2016 soybean residue was worked before April 15th are at much less risk for black cutworm damage to the 2017 crop. Larvae from this flight could be large enough to cut small corn or sugarbeets in as few as 3 weeks, but the forecast cold weather will slow down both cutworm larvae and corn emergence.

As of now, it looks the highest probability for any threatening populations is in the western Brown, eastern Redwood Co. area. In this area, you may want to plan on scouting later-tilled or minimum-tilled fields and fields with heavy spring weed populations or cover crops a bit harder. Corn with the Cry1F (Herculex I) or Vip3A (Viptera) traits are less susceptible, but not immune, to cutworm damage.

NOAA storm system radar from April 15, 2017

Figure 3. Precipitation on April 15th, 2017. The SW side of the band of heavier rain is where the larger moth captures occurred. Moths are not transported in all weather systems from the south.

I’ll start predicting potential cutting dates after this cold snap is over. 

There is still time for some significant migration to occur.

Until next week,

Bruce Potter and Travis Vollmer