I often joke that rust can be cured with an oily rag and is encouraged by wet weather but this is at least part true when it comes to the fungal diseases that affect plants. I was lucky last year and there was not a lot of rust apart from on the groundsel (Senecio vulgaris) I had let grow where I got a bit behind wit the weeding. But as i was clearing the last leeks from the ground yesterday, to finally make room and get the ground ready for sowing the next crop, I noticed that the last batch were badly affected by this common disease.
Rusts are generally host-specific although some have an alternate host spending part of their life cycle on a second, unrelated plant. So the rust on your roses will not spread to your hollyhocks or leeks.
Leek rust (Puccinia allii) is generally more common in late summer and shows as orange pustules (raised spots) on the leaves. It rarely affects the shaft (which you eat) and it does not often damage the plant much, though if the disease strikes early it causes the outer leaves to wither and looks pretty nasty. In general it is encouraged by wet weather, overcrowding and too much nitrogen in the soil. Although it can spread to chives and garlic it is not common for it to spread to onions. But I am not sure how it may spread to the many ornamental onions I have planted so i was keen to get rid of this before it got worse. So all the leeks were harvested and the foliage disposed of.
There are no chemical sprays you can use but there are some varieties that are more resistant to the disease. These include (but there are more) ‘Oarsman’ , ‘Autumn Giant 2’, ‘Sultan’ and ‘Malabar’.
The disease doe not live on dead leek foliage but only on living plants so good hygiene can go a long way to eliminating it or at least reducing it in the garden.