Puccinia allii

Leek rust is a disease caused by the fungus Puccinia allii. Most important on  leeks but also affects onions, garlic, chives and other Allium spp. The rust pathogen is comprised of genetically distinct sub-groups which differ in different parts of the world.  In the UK onions are rarely severely affected, but rust can be serious on leek, garlic and chives. Most attacks occur from mid-summer until late autumn.

You may see the following symptoms:
On leaves: Bright orange pustules on both sides of infected leaves. These are initially enclosed by the surface tissues of the leaf, but break open to release dusty, orange, airborne spores
Severe attacks may cause leaves to shrivel prematurely and will reduce vigour

Non-chemical control
Infection is worse on nitrogen-rich soils with low potassium, so take care with fertiliser applications
Do not crowd plants, as this raises humidity and increases the likelihood of infection
Dispose of all plant debris at the end of cropping
Suppliers sometimes claim a degree of resistance for certain varieties, check the latest catalogues for those currently available

Plant Protection Products