2025 University of Minnesota Cooperative Black Cutworm Trapping Network
Report #1 March 28-April 4, 2025
This issue was prepared by:
Dr. Fei Yang – Extension Corn Entomologist, University of Minnesota Department of Entomology
Bruce Potter – Potter Brothers, LLC and University of Minnesota Extension retired
April 8, 2025
Greetings,
The information on 2025 moth migration provided by pheromone trap cooperators in this network can help predict potential for black cutworm outbreaks in Minnesota. There are several moving parts to an economic infestation by black cutworms. This network will provide information on the timing and abundance of arriving moths.
Last week’s weather systems were not favorable for moth migration into Minnesota and the operating black cutworm pheromone traps did not capture any moths. Additionally, any arriving moths would have found most nighttime temperatures too cold for activity.
What conditions are needed for crop-threatening black cutworm (and armyworm) populations in Minnesota?
1) Migrating moth populations in overwintering areas. Black cutworms (Agrotis ipsilon) and armyworms (Mythimna unipuncta) cannot survive our northern winters but can survive and and reproduce as far north as topsoil remains unfrozen. Unusually cold winters can limit these populations.
2) Weather conditions to aid migration north when moths are ready to migrate. From late March through May, look for a cool, dry low-pressure system in western plains meeting a high-pressure system bringing warm, moist Gulf air to the east. The rotation produced by the two systems’ interaction creates strong southerly flows. These “low-level jet streams” are especially strong at night and met by migrating flying upward to meet them. The moths riding these systems often fall out with rain on the back side of thunderstorms passing through Minnesota.
3) The arriving moths find good sites to lay eggs and spring weather conducive for egg and larval survival. Moths, larvae, and to a lesser extent eggs, cannot survive freezing weather. Female black cutworm moths prefer low laying areas with winter annuals (e.g. shepherd’s purse) or early emerging annual (e.g. common lambsquarters) weeds. Armyworm moths are attracted to vigorously growing dense grasses (e.g. pastures, weeds, winter cereal crops) to lay eggs.
What do the black cutworm and armyworm pheromone traps capture and measure?
Unmated, female moths mate on arrival. Only male moths, attracted to a species-specific synthetic pheromone that mimics that produced by the female are captured by these traps. The pheromone traps are only effective for the few nights unmated migrant males are active.
The pheromone trap captures provide information on when, and where, moths arrive and estimate the size of the migration event(s). This information can be used to predict where, and using degree-days, when crop-threatening infestations can occur.
Unlike the pheromone traps, blacklight insect traps collect both sexes for as long as the moths live. They may capture larger numbers of moths over a longer period. Blacklight trap captures have not been correlated with the risk of black cutworm larva outbreaks, but they may be more predictive than pheromone traps for armyworms. Differences in biology of the two may explain the differences.
For more information on migration, and other management facts of these two crop pests, see
Corn-pest-management/Black-cutworm-corn and
Corn-pest-management/armyworm.
For more information: bcw-reporting
This network is supported, in part, by the farm families of Minnesota and their corn check-off investment.
Contact me with any questions and Happy trails,
Bruce Potter
[email protected]
(507) 276-1184