Alfalfa looper – caterpillar, damage AAFC

Hosts

Prefer alfalfa, clover, and lettuce. Other hosts include canola, peas, spinach and various garden crops, ornamental trees, and tree fruits.

Identification

ADULTS: Dull grey or brown bodied moth with silvery-grey forewings (30–38 mm wing span), each with a distinct yellowish sickle-shaped spot near its centre.

Looper, alfalfa

MATURE LARVAE: 25 mm long, light to olivegreen with paler head and slightly swollen abdomen; walk in a looping fashion (3 pairs of prolegs).

Lepidoptera

Autographa californica Speyer

Feb

Overwintering

Mar

Apr Eggs

May

June

Larvae

July Pupae

Aug

Sept

Oct

Migrating Adults

Nov

Dec Adults

Immigrating Adults Eggs Larvae Pupae

Beat canola plants in an area 50 cm x 50 cm and record the number of larvae on the ground. Repeat this procedure several times in different locations to obtain an average number of larvae per square metre for the field.

Economic Threshold

No economic threshold has been established in canola. However, more than 15 larvae per square metre, combined with heavy defoliation or flower and pod clipping, may warrant control.

Management Options

Life Cycle

BIOLOGICAL: A virus disease causes significant mortality of first generation 5th–6th instar larvae, terminating most infestations. Infected larvae hang from host plants dripping virus-infested body fluids that infect other larvae. Several species of generalist predators and some parasitoids attack eggs and larvae.

Feeding Damage

CULTURAL: For alfalfa, harvest as soon as noticeable defoliation occurs. Watch regrowth for larval feeding injury.

LARVAE: Canola—First generation larvae feed along leaf margins and may defoliate a large portion of the plant as well as clip flowers and seed pods. Infestations are usually patchy and during flowering. Second generation larvae are usually not a problem (see below).

CHEMICAL: Control products available but rarely required for protection of canola or alfalfa crops.

Most moths seen in the spring blew in from the U.S. although some may have emerged from the few pupae overwintering in the soil. Two or three overlapping generations of larvae per year depending on weather conditions. Jan

Monitoring/Scouting

ADULTS: Feed on nectar from flowers and are active during the day.

Alfalfa—Similar injury as for canola; first cut regrowth at risk under high population pressure.

Similar Species Jan . Feb . Mar . Apr . May . June . July . Aug . Sept . Oct . Nov . Dec !

Adults can be confused with the cabbage looper (Trichoplusia ni (Hübner)) and celery looper (Anagrapha falcifera (Kirby)); alfalfa caterpillar (Colias eurytheme Boisduval (p. 81)) and imported cabbageworm (Pieris rapae (Linnaeus) (p. 80)) may also be present. Alfalfa looper – cocoon AAFC

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Alfalfa looper – adult

Peggy Greb, USDA Agricultural Research Service, Bugwood.org

Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management Field Guide