Cabbage maggot – adult Tyler Wist, AAFC

Canola, mustard, cabbage, rutabaga, radishes, cauliflower, and broccoli. Cabbage maggot is the most common species attacking canola.

MATURE LARVAE: 8 mm long, whitish maggots.

Economic Threshold

Overwinters as pupae in the soil of host crops. Each female lays up 200 elongate white eggs at the base of host plants. Usually one generation, but two overlapping generations are possible during warmer or extended summers.

Feb

Mar

Overwintering

Overwintering Pupae

Apr Eggs

May

June

Larvae

July Pupae

Aug

Sept

Oct

Nov

Dec

Adults

Adults Eggs Larvae

None established.

Management Options

ADULTS: None; feed on the nectar of various flowers.

BIOLOGICAL: Several species of predators and parasitoids attack all root maggot life stages and provide the greatest protection against root maggot depredation in canola. Carabid (p. 111) and rove beetles (e.g. Aleochara bilineata Gyllenhaal (p. 113)) feed on eggs, larvae, and puparia; nematodes attack the larvae. Some fungal and bacterial pathogens also provide some control.

LARVAE: Infestations and damage are more severe under cool, damp soil conditions. Larvae feed on the roots of seedlings and developing host plants; mature larvae create channels on or tunnel into tap roots causing lower leaves to turn yellow. Damage may also promote disease that further affects plant growth. Heavy infestations can delay blooming and cause severe lodging and yield losses. Infested canola roots are often darker than normal roots. Damage is more severe under cool temperatures and wet soil conditions.

CHEMICAL: None registered in Canada.

Feeding Damage

Jan

Monitoring/Scouting

Scout for the presence of all adult root maggots starting in mid to late May using yellow sticky cards or sweep nets.

Life Cycle

Delia radicum (Linnaeus)/Delia floralis (Fallen)

Seedcorn maggot (Delia platura (Meigen) (p. 40)).

Identification

ADULTS: 4–6 mm long, light gray flies; wings overlap when at rest.

Maggot, cabbage/turnip

Similar Species

CULTURAL: Rotate host crop with non-host crop. Avoid planting Brassica rapa (Polish canola) cultivars which are more susceptible to damage than B. napus (Argentine canola) cultivars and brown and yellow mustards. Increased seeding rate and row spacing can decrease root maggot damage. Spring and/or fall tillage may reduce fly emergence by exposing puparia to predation. In some instances severely damaged crops could be ploughed under and immediately reseeded.

Diptera

Hosts

PESTS

Jan . Feb . Mar . Apr . May . June . July . Aug . Sept . Oct . Nov . Dec ! Cabbage maggot – larva, damage

Mike Dolinski, [email protected]

Descriptions of Field Crop Pests

39