On 7/18/2016 1:14 PM, Frank wrote:

I'm having the same problem. Maybe spraying in advance next year
might prevent it but I hear once in the soil there is nothing to do
except replace the soil.

Fungus spores can be spread by wind, rain, creatures. It most commonly
is found in the soil, and gets splashed up onto the plant leaves with
rain or watering, so mulching helps minimize it. Also space the plants
widely to minimize transmission between plants.

There used to be a soil fumigant available for retail sale that
completely killed everything in the soil. It was useful in the last
resort and would provide fungus-free gardening for several years
before the spore counts invariably increased again. But it was taken
off the market, as it was quite hazardous to handle.