Biology and control of the pea midge

Pea midge larvae feed within the developing buds, reducing yield by preventing pod formation and causing distortion of the growing point. Vining peas can be more susceptible than combining peas.

• Increased risk in areas where peas have been grown previously
• Vining peas can be more susceptible than combining peas
• Crops are most susceptible at the early green-bud stage
• From the Humber northwards, vining peas may not be attacked until late June, so early crops may escape serious damage

Scientific name: Contarinia pisi

Adults are gnat-like flies with a yellow-grey body. They are about 2 mm long with long legs. The head is dark, with very fine antennae. The semi-transparent wings are slightly longer than the body and folded together along its back, when at rest.

Eggs are approximately 0.3 mm long, oval with a tail-like tip and have a translucent, jelly-like appearance.

Larvae are dirty white and 2–3 mm long when mature.

Sep–Apr: Larvae overwinter in soil in cocoons.

May: Larvae pupate. Some may remain in the soil for 1 year or more.

Jun: First-generation adults emerge and lay eggs in batches on the rudimentary buds and leaves surrounding them. Hatching larvae enter buds to feed. They may also feed in the clustered leaves of the terminal shoot and the pods.

Jun–Jul: First-generation larvae drop into the soil. Some pupate to create a second generation, while others remain to overwinter.

Jul–Aug: Second-generation adults emerge and lay eggs on the crop. Hatching larvae enter buds to feed.

Aug–Sep: Second-generation larvae drop into the soil to overwinter.

Infested buds become swollen, gouty and do not produce pods, thus reducing yield. Leading shoots may also become deformed, limiting their extension growth and producing a ‘cabbage’ or ‘nettle-head’ appearance. In wet periods, damaged tissue may also provide a site for infection by fungi such as Botrytis spp.

Non-chemical control

Cultural controls include early spring sowing, the selection of early varieties, crop rotation and deep ploughing to bury the overwintering larvae. Avoid sowing peas on land adjoining previously infested land.

The bright red larvae of the midge Lestodiplosis pisi prey on pea midge larvae. Several parasitoids have also been identified.

Monitoring

A pheromone monitoring system is available comprising four sticky traps with pheromone lures. Place traps 10 m apart in the previous year’s pea field by the third week of May to monitor adult emergence from overwintering sites. Inspect traps at least twice weekly and replace the sticky cards each time.

Thresholds

If more than 500 midges are caught on one trap, nearby susceptible pea crops should be examined (as late in the day as possible) for the pest.

Insecticide resistance

None known.