Armyworms have been steadily moving across Kentucky and will likely be with us until frost. The lifecycle of armyworms is approximately 20-30 days (from eggs, to worms, to pupae, to moths, to eggs again), but it is important to remember that the population is NOT synchronized. So new armyworms could be emerging daily until frost. We wanted to share a few observations and thoughts with you.
We are observing plenty of egg laying from the current crop of armyworms. This is a good indication that they will be a persistent problem until frost. Alfalfa and clover seem to be a preferred food source, but there are also reports of devastated hayfields and pastures. We expect established hay and pasture stands to grow back normally, but may be weakened.
Controlling re-infestations in alfalfa is critical as we move into fall. As you know, allowing alfalfa to replenish carbohydrate reserves in the taproot prior to fall dormancy is important for persistence and growth in the spring. So, scouting and insecticide application when the economic threshold has been reached is critical to the the long-term health of alfalfa stands.
If you are establishing new forage stands this fall, it is critical that they are closely monitored, and insecticides are applied as soon as the economic thresholds have been reached. New seedings will be extremely susceptible to fall armyworm damage since they do not have an established root system and will not likely recover. If you are stockpiling cool-season grasses for winter grazing, it will be important to closely monitor growth for armyworms and apply insecticide once the economic thresholds have been reached.
~ Chris Teutsch and Ray Smith