Wheat Bulb Fly

Biology

Adult Wheat Bulb fly are small, weakly flying insects similar to small houseflies. They are normally present from mid-June to September and lay eggs on bare soil between mid-July and early September. Eggs need cold weather to break diapause and hatch in late December and January.

Larvae are white and legless with obvious black mouth hooks at the pointed head end. The rear end is blunt and carries six lobes. They burrow into the base of cereal plants and move upwards. Wheat Bulb fly larvae grow very quickly in March and April and can reach 12mm in length. These larger larvae then move to adjacent shoots causing further damage. Feeding ends in early May and larvae then pupate in the soil. Approximately 40% of eggs laid result in larvae attacking shoots. There is only one generation of Wheat Bulb fly per year.

Attacks are worst where there is bare soil, especially if freshly cultivated, for egg laying during July and August. Wheat crops following fallow or ploughed set-aside, potatoes, vining peas, sugar beet and onions are most at risk. Wheat Bulb fly do not move very far and tend to predominate in the eastern counties of England where crop rotations particularly suit their life cycle. However, attacks do occur in eastern Scotland, Lancashire and the Cotswolds.

To minimise the risk of attack from Wheat Bulb fly avoid leaving bare soil in July and August. Rotational choices could include drilling winter oilseed rape after set-aside or switching to spring sown cereals. If winter cereals are drilled late consider the use of an appropriate seed treatment and avoid drilling too deeply.

For more information on control options for wheat bulb fly, click here.