By John Tooker
Trap data and growing degree-day models indicate this should be started in some areas of the state.
With abundant detections of black cutworm moths by Penn State Extension’s Black Cutworm Monitoring Network, the risk of damage to corn from black cutworm caterpillars appears to be elevated. At the site where we detected the first significant flight of moths (Franklin County), degree-day accumulations range have reached 236, so if we get some warm weather within the next week 300 degree days could be reached for that area and it would be time to scout for cutting damage (Table 1). The other sites around the state range from 90-170 degree days (Table 1). After 300 degree-days, I recommend farmers scout fields for cutting damage.
Table 1. Degree-day accumulations through 23 May 2016 in eight regions in Pennsylvania that experienced significant flights of black cutworm moths. When 300 degree days accumulate at each site from the day of the flights, cutting damage can be expected to be evident in fields—this is when scouting should occur.
| County | Closest town | Accumulated degree days |
|---|
| | | |
| Berks | Kutztown | 125 |
| Centre | Rebersburg | 110 |
| Clinton | Loganton | 102 |
| Elk | St. Mary | 89 |
| Franklin | Fayetteville | 236 |
| Lebanon | Cornwall | 167 |
| Lycoming | Montoursville | 145 |
| Potter | Ulysses | 90 |
Because caterpillar populations are notoriously spotty, I would not recommend using the elevated risk as a justification for adding insecticide to a tank mix unless you have confirmed that damage exceeds the economic threshold. Insecticide applications not targeted and timed appropriately will not be effective, and will probably waste money. While some Bt varieties can be helpful for managing black cutworm, seed treatments are not very effective. Rescue treatments are usually the most efficient and economical tactic for managing black cutworm. For more information, see our factsheet.
Source:psu.edu