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
