I don't really know, but since no one else answered, I will take a stab at it.
Re the virus I found this:
There are at least 27 different viruses that have been identified in dry peas. Of these, pea enation mosaic virus (PEMV) and bean (pea) leaf roll virus (BLRV) are two major pathogens that can cause significant damage under favorable conditions. PEMV and BLRV survive from year to year in alternate crops such alfalfa, chickpea, clover, pea, vetch and some weed species. BLRV and PEMV are not seedborne and can only be transmitted by aphids.
So it sounds like the virus is not in the soil and what you need is to be very careful about the presence of weeds and aphids.
The downy mildew is very virulent and DOES remain in the soil. In most areas of the country it does not over winter in the soil, doesn't tolerate the freeze. Where you are it may over-winter also. Here's an article about downy mildew in cucumbers.
It suggests Neem oil and hydrogen peroxide as treatments. I would try making up a dilute solution of the peroxide and using it as a soil drench before you plant.