Cabbage seedpod weevil – adult

Alberta Agriculture and Rural Development

TRUE (LARVAL) HOSTS: Canola, brown and wild mustard ADULT HOSTS: Cole crops and flixweed, stinkweed, and hoary cress. Yellow mustard is not a host.

Identification

ADULTS: 3–4 mm long, with long narrow snout. Play dead when disturbed.

Weevil, cabbage seedpod

MATURE LARVAE: 2–3 mm long with whitish body, brown head and anal plate, and 3 pairs of thoracic legs.

Ceutorhynchus obstrictus (Marsham)

Life Cycle

Jan

Feb

Overwintering

Mar

Apr

May

Eggs

June

Larvae

July Pupae

Aug

Sept

Oct

Nov

Dec

Adults

Adults overwinter under plant material along field margins and emerge beginning in April to feed and mate; females lay up to 250 eggs in pods, usually only one egg is laid/pod. Larvae feed for about 6 weeks then drop to the ground to pupate in earthen cells. One generation per year.

Economic Threshold 3–4 adults/sweep.

Management Options

BIOLOGICAL: Minimal impact on populations. Two species of parasitoids: Microctonus melanopus Ruthe, a wasp that parasitizes adult weevils (p. 126); and Trichomalis perfectus (Walker), a wasp that attacks weevil larvae within the pods (p. 133). CULTURAL: Plant a trap crop of an earlier flowering canola variety, or seed a trap crop of the same variety 7–10 days earlier in order concentrate emerging adults along field margins for more efficient insecticide treatment if warranted. CHEMICAL: For best results, make first treatment when the crop is in 10–20% flower (70% of plants have minimum 3–10 open flowers) to reduce egg laying in newly formed pods. Spray later in the day when bees and other beneficials are less active.

Feeding Damage

ADULTS: Cause bud-blasting from feeding on developing flower buds and young flowers which generally does not affect yields. Adults will also feed on pods in late canola crops.

Overwintering Adults Eggs Larvae

Pupae

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

Coleoptera

Hosts

PESTS

LARVAE: Feed on developing seeds (up to 5/larva over 2–3 week life span); infested pods are more susceptible to shattering and fungal infections that further reduces marketable yields.

Similar Species

Ceutorhynchus neglectus Blatchley—smaller weevil (2–3 mm) present at same time on canola.

Monitoring/Scouting

From early bud stage through flowering, take ten 180° sweep net samples at ten sites following a “W” pattern across the field from a field margin.

Cabbage seedpod weevil – larva

Cabbage seedpod weevil – damage

Mike Dolinski, [email protected]

Mike Dolinski, [email protected]

Descriptions of Field Crop Pests

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