Bruce Potter, IPM specialist
Leaf feeding on emerged corn or weeds will be visible for the next week or so. By the last few days of May and early June, larvae will be large enough to cut off small corn plants (Table 1). Corn cut above the growing point will recover. The concern is the black cutworm’s tendency to cut plants below the soil surface and growing point. Unlike corn, the growing points of broadleaf crops such as sugarbeets and soybeans are aboveground at emergence and these crops are susceptible to both subterranean and surface feeding cutworm species.
Fields with the following criteria are at higher risk from black cutworms. Pay close attention to any depressional areas in the field.
This project is supported, in part, by the farm families of Minnesota and their corn check-off investment.
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| Black cutworm damage to a young corn plant. Photo: W.M. Hantsbarger, Bugwood.org. |
To this point in 2022, migratory flights of black cutworm moths into Minnesota have been relatively light. However, from April 29 to May 1, significant captures (eight or more moths/two nights) were detected in six counties. These captures followed weather systems and rainfall patterns through the SW part of Minnesota (Table 1). It is important to include cutworms in your scouting efforts as you are evaluating crop and weed emergence. Continued delayed planting in some areas continues to prolong the risk for late-arriving moths.
Leaf feeding on emerged corn or weeds will be visible for the next week or so. By the last few days of May and early June, larvae will be large enough to cut off small corn plants (Table 1). Corn cut above the growing point will recover. The concern is the black cutworm’s tendency to cut plants below the soil surface and growing point. Unlike corn, the growing points of broadleaf crops such as sugarbeets and soybeans are aboveground at emergence and these crops are susceptible to both subterranean and surface feeding cutworm species.
Fields with the following criteria are at higher risk from black cutworms. Pay close attention to any depressional areas in the field.
- Spring tillage or planting after May 1.
- Soybean previous crop.
- Strip or ridge-tillage
- Field history of heavy winter annual (e.g., shepherd’s purse, pennycress) or early emerging annuals (e.g., lambsquarters) or other early-season vegetation.
- Fields in or near counties with significant captures.
- Corn hybrid without a Herculex® I or Viptera® above-ground Bt trait .
- Fields without a chlorantraniliprole or neonicotinoid seed treatment or rootworm insecticide.
Table 1. Black cutworm feeding and cutting projections based on historical average temperatures. Midwest Regional Climate Center U2U https://mygeohub.org/groups/u2u/purdue_gdd
| County | 2 night capture |
Biofix date |
Approx. post-flight degree-days as of May 5 |
Estimated current max BCW stage |
Est. start corn leaf feeding1 |
Est. start corn cutting2 |
Projected end of cutting3 |
|---|---|---|---|---|---|---|---|
| Lincoln | 10 | Apr 29 | 159 | 1st-3rd instar | May 13 | Jun 3 | Jun 22 |
| Murray | 7* | Apr 29 | 155 | 1st-3rd instar | May 13 | Jun 4 | Jun 22 |
| Nicollet | 10 | Apr 29 | 193 | 1st-3rd instar | May 11 | May 29 | Jun 17 |
| Nobles | 11 | Apr 29 | 166 | 1st-3rd instar | May 13 | Jun 2 | Jun 21 |
| Nobles | 10 | Apr 30 | 163 | 1st-3rd instar | May 13 | Jun 2 | Jun 21 |
| Renville | 11 | May 1 | 163 | 1st-3rd instar | May 13 | Jun 3 | Jun 22 |
*Less than a significant two-night capture
1Based on 90 degree-days (base 50F) after significant flight (leaf feeding begins).
2Based on 312 degree-days (base 50F) from significant flight.
4th-6th instar larvae are large enough to cut corn. Small plants, e.g. sugarbeets, can be cut earlier.
3Based on >641 degree-days (base 50F) after significant flight pupation.
For more information on black cutworm and weekly updates see the black cutworm reporting network.
This project is supported, in part, by the farm families of Minnesota and their corn check-off investment.
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