If it were me, I would do three things:
Get up all that blighted vegetable matter, compost it thoroughly, and return it to the soil. I would say to use the J. Jenkins method of composting though, if you can

. This is all about Biodiversity and is a little extra work yes, however you are 'priming' the soil with good 'ole compost microbes. The spores, eggs, and seeds of undesirables will be purged while the compost does its magic. Apply it lasagna method, or any old method you deem necessary.
If you clean up any woody plants, go ahead and pyrolyze them, Mix that compost 50/50 with some charcoal you just made let it set for a couple of weeks and then you have Bio-char.
Mulch, mulch, mulch. Mulch under the soil (hugelkultur) Mulch over the soil. Mulch as it breaks down over the years brings nutrients, retains water, provides humus, and beneficial fungi love to munch on lignin (the collagen like substance of the plant world).
Yes you can spot check the soil with this or that technique, but in a good permaculture system, just like in a working ecosystem, Soil is the Key. If your soil retains water, everything gets a hell of a lot easier. Biologically active Charcoal and Rotted Wood are great, low impact ways to get the soils starting to hold water. Once the soil is healthy, you will find that the plant diseases will be reduced to an acceptable level.