By Christian Krupke
• New traps for armyworm, far more effective in capturing moths.
• Armyworm both migrate and overwinter in Indiana.
• Mated female moths are looking for lush, tall grasses to lay eggs.
This year, we have installed Hartstack traps at each of the Purdue Ag Research Farms to monitor the flight of armyworm in the spring and early summer. The Hartstack trap (also known as Texas cone trap), is a large, bulky, and expensive wire mesh trap used also to monitor corn earworm flights. Up until this week, the captured numbers have not been too impressive, but it’s obvious that the recent warmer temperatures have this species on the move; refer to the following “Armyworm Pheromone Trap Report.”
Although it is suspected that most armyworm moths migrate into the Midwest from southern states, similar to black cutworm, rising winter temperatures indicate that overwintering here in the Hoosier state is increasingly likely. This may explain why traditional small grain/grass forage growing areas of the state often have higher moth counts. Nonetheless, the important issue is that moths are now plentiful, actively flying, and seeking mates and egg-laying sites. In armyworms, the populations of adults are evenly male and female; so we use the male-only catches in pheromone traps to estimate the female numbers.
Hartstack trap.
Once mated, female moths begin seeking favorable egg-laying sites. Those areas, deemed high-risk for oviposition are dense grassy vegetation (e.g., wheat, grass hay, grass cover crops). With the increase in cover crop adoption, it has been found that cereal rye grass is a favorite for armyworm. That being said, any lush grasses are likely being visited by armyworm moths this and subsequent weeks, until the cover is terminated. If the grass cover crop is terminated at least 10-14 days before planting corn, then the small armyworm larvae will likely starve before the corn emerges. The larvae prefer grasses but will eat anything they can if hungry. Armyworm will attempt to feed on any live plant (e.g., both crops and weeds) once their food source has been killed. However, they will not thrive on broadleaves, such as soybean, initially causing damage, but they will eventually die out from poor nutrition.