Loopers

Alfalfa looper and cabbage looper larvae are green caterpillars with three pairs of true legs in the front and two pairs of robust, unjointed prolegs on the abdomen (back portion of the body). A distinguishing characteristic of looper caterpillars is that as they crawl, they move their rear end up toward their heads so their body arches into a circular loop. Adult moths have dark brown, mottled forewings with a characteristic figure-eight marking in the center.

Loopers may occur at any time during the growing season. Infestations early in the season on seedling plants may result in damage to cotyledons, new leaves, and terminal buds. Looper eggs are deposited singly, usually on the underside of younger leaves. The larvae feed on larger, more mature leaves.

Loopers have many natural enemies that frequently keep them below economically damaging levels, unless the natural enemies are killed by insecticide applications applied for other pests. Important parasitoid wasps include the tiny egg parasitoid, Trichogramma pretiosum, and four wasps that attack the caterpillars: Hyposoter exiguae, Copidosoma truncatellum, Microplitis brassicae, and Cotesia medicaginis (alfalfa looper only). In addition to the parasitoid wasps, a tachinid fly, Voria ruralis, also attacks the caterpillar. In some areas, the nuclear polyhedrosis virus, an important biological control agent, occurs naturally in fields and kills loopers. Plant habitat that attracts natural enemies and avoid the use of broad-spectrum pesticides known to harm natural enemies.

Use biological control, Bacillus thuringiensis, and the Entrust formulation of spinosad for an organically certified crop.

Start inspecting plants for looper damage during the vegetative growth stage. Continue monitoring from flower bud to bloom and during the pod fill stage.

Specific treatment thresholds have not been established for loopers. Late-season infestations do not usually cause significant crop loss. If damaging numbers during mid-season results in excessive foliage loss, an insecticide application may be warranted to prevent crop loss.