Certified GKH Gardening Expert
There are many fungicides on the market, and they all work pretty decently. You have your choice there, although having soil sampled and finding out exactly what it is will give you the best method to kill it off.
I like to use a method that kills off infection, while leaving the soil more nutritious and healthy than before the infection. That can't be said for synthetic fungicides. Using dolomitic lime and wettable sulfur in tandem will take care of most infections, unless they are not able to be killed, such as Mosaic Virus. That is a permanent soil issue that can only be gotten around, not killed.
Fortunately diseases like this are plant or genus specific, so they don't tend to infect other types of plants.