They may be olive green to almost black in color down the middle of the back with a yellow stripe on each side of the body. Armyworms may become abundant and cause severe injury to alfalfa hay in the summer and fall. First and second instar larvae tend to feed in clusters around the egg mass from which they hatch. This frequently causes a tattered appearance to the terminals.
Chemicals are necessary when economic populations are present and it is too early to cut.
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies. Do not apply when bees are present. Formulations such as Dipel do not control beet armyworm. Does not harm beneficial insects. Repeat treatment as necessary.