Spider mites want dry conditions. spray off foliage regularly and encourage predators by not using pesticides to prevent spider mites.

Mulch fallow beds with a thick layer of quality compost and let them sit as long as possible, then work the compost into the soil a month or so before planting.

Something to enrich the soil is helpful -- mulch or cover crop, your choice.

Something to discourage mites must occur during the growing season.
Spider mites are on stressed plants.
Spider mites are *not* in the soil.

I do what Hoov suggests using manure. I doubt you can rid your vegie garden of pests. Ever. I handpicked caterpilars off cabbage this year and lost. Never had planted it before. Tomatoes were there previously. And I've never had a horned tomato caterpillar! Go figure.

Powdery mildew on squash leaves? I think that's mandatory. :-) You might read up on sulfer dust.

Thanks everyone. Yes, I have no illusions about getting rid of pests entirely. ;) And it does seem like powdery mildew is almost inevitable here - the folks at my nursery seem to agree. The only reason I worried was that there were so many mites....(like giant orange colonies - I will spare this forum the picture but I've never seen anything like it)

Would you all agree that I should let the beds lie fallow then or should I just go ahead and plant winter veggies? I think some of the people suggesting that in the Garden Clinic assume that winter is a lost season anyway - but for us it is still a growing season so I'm wondering if that's appropriate advice.

Jean you said they'll just die on the soil right? So do you think think I need to let them lie fallow? Or just move on and put in winter crops?

Inorder for mites to survive, they must be on live plants.
They're a common pest of stressed plants during hot, dry weather/conditions.
They don't bother plants in the winter unless those plants are in a protective structure -- greenhouse, solarium, etc.

Suggest you plant winter stuff -- if there's still time. It *is* getting late even though you're in SoCal.

okay thanks jean. going to make my seed tape then. ;)