In peas, the larvae curl up and are a contaminant in processing. This pest is distributed throughout the United States and parts of Canada. The alfalfa looper overwinters as a pupa either in the soil or in trash near the base of host plants. Eggs hatch in three to five days, and the larvae feed for about two weeks before pupating in cocoons on the host plant or in trash. The total development time from egg to egg requires about 30 days.
Adults emerge in about seven days, mate, and females deposit eggs about three days after emerging.
Damage is most evident in June and July and again in September and October. There are three or four generations each year. The alfalfa looper population is often reduced by a virus disease and several predators and parasites, but the populations of natural enemies may not be sufficient to reduce heavy infestations. Insecticides are commonly used to prevent damage by this pest, but fields should be sampled prior to treatment to establish the need for treatment. Insecticides are much more effective against early instar larvae.