article Sep 11, 2016
In typical seasons growers can see two peaks of armyworm activity, Espino says. The first tends to be in mid-to-late June and the second in mid-August. The first period tends to result in defoliation while the second period tends to injure the panicle, resulting in blank grains.
Espino says rice can tolerate some defoliation and still not affect yield. The recommended threshold for defoliation is 25 percent. Beyond that Espino says yield loss can occur.