Dr. Fei Yang – Extension Corn Entomologist, University of Minnesota Department of Entomology, and
Bruce Potter – Potter Brothers, LLC and University of Minnesota Extension retired
Again in 2026, the University of Minnesota Black Cutworm and Ture Armyworm Cooperative Trapping Program will track the migration of black cutworm and armyworm moths into Minnesota. This project is funded by Minnesota farm families and their checkoff dollars.
University and industry cooperators check their pheromone traps each day. Their trap captures help us determine the timing and relative size of moth arrivals into Minnesota. These data are helpful in identifying the timing and location of moth migrations that might threaten corn and other crops. Trap data and degree-days for larval development are analyzed each week, and updated on https://z.umn.edu/bcw-reporting.
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.
One of spring’s visible signs of insect migration from the south is the arrival of red admiral and painted lady butterflies.
For more information on migration, and other management facts of these two crop pests, see https://extension.umn.edu/corn-pest-management/black-cutworm-corn and https://extension.umn.edu/corn-pest-management/armyworm.
For more information: https://z.umn.edu/bcw-reporting
This network is supported, in part, by the farm families of Minnesota and their corn check-off investment. Products are mentioned for illustrative purposes only. Their inclusion does not mean endorsement and their absence does not imply disapproval.
Bruce Potter – Potter Brothers, LLC and University of Minnesota Extension retired
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| Early (2nd) instar black cutworm and its leaf feeding on 1-leaf corn. Photo: Bruce Potter |
University and industry cooperators check their pheromone traps each day. Their trap captures help us determine the timing and relative size of moth arrivals into Minnesota. These data are helpful in identifying the timing and location of moth migrations that might threaten corn and other crops. Trap data and degree-days for larval development are analyzed each week, and updated on https://z.umn.edu/bcw-reporting.
What conditions are needed for crop-threatening black cutworm and armyworm populations in Minnesota?
- Migrating moth populations in overwintering areas. Black cutworms (Agrotis ipsilon) and armyworms (Mythimna unipuncta) cannot survive our northern winters but can survive and reproduce as far north as topsoil remains unfrozen. Unusually cold winters can limit these populations.
- 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 to the east bringing warm, moist Gulf air. The rotation produced by the two systems’ interaction creates strong southerly flows. These “low-level jet streams” are especially strong at night with migrating moths flying upward to meet them. The moths riding these systems often fall out with rain on the back side of thunderstorms passing through Minnesota.
- 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.
One of spring’s visible signs of insect migration from the south is the arrival of red admiral and painted lady butterflies.
For more information on migration, and other management facts of these two crop pests, see https://extension.umn.edu/corn-pest-management/black-cutworm-corn and https://extension.umn.edu/corn-pest-management/armyworm.
For more information: https://z.umn.edu/bcw-reporting
This network is supported, in part, by the farm families of Minnesota and their corn check-off investment. Products are mentioned for illustrative purposes only. Their inclusion does not mean endorsement and their absence does not imply disapproval.
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