White Blister on Brassicas

Hi,  I have just discovered that my brassicas have white blister.  They have been getting this for the last 3 years but I only found out what it was yesterday.  I always thought it was some kind of insect making a white coating over itself, or something like that!  I have been putting the old leaves in the compost bin, didn't realise it was a fungus and am now worried that I will spread it around when I use the compost.  I read that white blister mainly only affects brassicas so will it be alright to spread the compost around on the flower garden.  I don't grow wallflowers, which are in the brassica family.  I really don't want to throw all my hard won garden compost away.