White rust on cabbage

Has anyone had a problem this yr?i only noticed today that my cabbages grown near the tree hedge had white hard tiny lumps on them,i googled when i got home and i think its white rust
I mainly grow them for my hens so im not too worried but i read that im not to grow cabbage here again,i was going to plant winter and spring cabbage in the same area but im unsure now what to do
The ones near the centre of the plot seem ok but i read it can spread



I will take a pic of affected ones tomo x
Any advice muchly appreciated,thanks x