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Rust - Leeks/Onions

Puccinia allii

Pathogen

Fungus

Hosts

Onions and leeks

Symptoms

Characteristic raised bright orange pustules visible on both sides of the leaves.

Development

First appears from mid-summer to late autumn. Can only survive on `live` plant tissue. Spores dispersed by both wind and rain. Resting spores can be produced but it is thought that the majority of outbreaks come from host plants bearing disease on live tissue throughout the year.

Favourable Factors

Warm, dry conditions with high humidity.

Importance

Widespread and more commonly associated with leeks than onions but can be found on garlic and chives. Severe attacks reduce plant vigour.

Control

  • Clean seed

  • Crop rotation

  • Spray fungicides at the first sign of infection

  • Remove infected green plant debris at harvest