Hessian fly

Mayetiola destructor

1. Identification

• Common name: Hessian fly
• Scientific name: Mayetiola destructor Say
• Order: Diptera
• Family: Cecidomyiidae

2. Pest description

• Very small adults (2–3 mm), delicate dark-brown midges.
• White, legless larvae that develop inside the leaf sheaths.
• Pupae shaped like a “grain of rice”, brown in colour.
• Red eggs, laid in rows along the young leaves.

3. Main hosts

• Wheat (main host).
• Barley, rye and other grasses may be affected.
• Young plants are more susceptible.

4. Symptoms and damage

• Curling and discolouration of the leaves.
• Reduced growth and stunted plants.
• Formation of “galls” or larval chambers at the base of the leaves.
• Reduced tillering.
• Breakage of the stems and small or sterile ears.
• Significant losses in winter cereals.

5. Biological cycle

• Two to five generations per year, depending on the climate.
• Adults emerge in spring and autumn.
• Egg-laying on young leaves.
• Larvae feed at the base of the leaves for 2–3 weeks.
• Pupation inside the leaf sheaths.
• Overwintering as a pupa (“flaxseed stage”).
• Cycle favoured by mild temperatures and high humidity.

6. Monitoring

• Observation of symptoms on young plants.
• Sampling of leaves for the detection of eggs and larvae.
• Yellow sticky traps can help in the detection of adults.
• Intensive monitoring in early spring and autumn.
• Recording of favourable conditions (moderate temperatures and humidity).

7. Management measures

• Cultural: crop rotation with non-host species; late sowing to avoid population peaks; destruction of crop residues; choice of less susceptible varieties.
• Biological: conservation of natural parasitoids; promotion of generalist predators; use of entomopathogens in the soil where applicable.
• Integrated protection: continuous monitoring; targeted treatments when thresholds are reached; appropriate management of sowing density; judicious application of authorised insecticides; integration of cultural practices to reduce pest pressure.

Bibliographic references

• EPPO Global Database – Mayetiola destructor.
• CABI Invasive Species Compendium – Mayetiola destructor.
• Harris, M. O. & Rose, S. (1990). Biology and ecology of Hessian fly.
• Ratcliffe, R. H. & Hatchett, J. H. (1997). Genetics and resistance in wheat.