How to identify wheat bulb fly in cereals

Learning to spot the signs of wheat bulb fly (Delia coarctata) will help you to gauge pest pressure and choose balanced management options for your cereal crops.
How to manage wheat bulb fly risk in cereals

Life cycle and symptoms of wheat bulb fly

The larvae of wheat bulb fly are white and legless. They have no distinct head. However, their front ends are pointed and their hind ends are blunt. Larvae bore into the base of the stem to feed, leaving a ragged entry hole.

Wheat bulb fly larva.

Feeding can cause tillers to die back and display ‘deadheart’ symptoms.

Wheat bulb fly causes deadheart symptoms in cereals.

Adults are slightly smaller than, but similar in appearance to, house flies.

The adult wheat bulb fly feeds on fungi on cereal ears.

This wheat bulb fly life-cycle illustration features in AHDB Project Report 624. It was created in BioRender by Daniel Leybourne at ADAS.

Wheat bulb fly life cycle
  1. Eggs laid on bare soil (Jul–Sep).
  2. Eggs hatch and larvae bore into crop stem-base to feed (Jan–Mar).
  3. Each larva attacks multiple tillers (Mar–Apr).
  4. Larvae emerge and pupate (Apr–May).
  5. Adults emerge from pupae, feed on saprophytic fungi on host plant and reproduce (Jun–Sep).
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Other larvae

Yellow cereal fly larvae are present at a similar time to wheat bulb fly. However, they are pale yellow with pointed ends, thinner and enter the crop through the top of the shoot. This results in a characteristic brown incision that spirals down the tiller. Unlike wheat bulb fly, each larva only attacks a single tiller. Frit fly larvae are present earlier in the season, with damage seen in September to January.

Learn more about the pests and natural enemies of field crops