I have a new raised bed veggie garden and two of my squash plants have separate disorders going on that I need help to identify and manage. 1) zucchini plant's older larger leaves have white patches on them. Does not appear 'powdery'. (they are irregularly shaped and are not visible on the underside) 2) summer squash plant has just developed small deep yellow spots on the leaves (the spots go through to the underside). Thanks for your help!
i am not sure what is wrong with your plants, but your soil needs work! i would add some compost and mushroom manure to bring up the soil to workable nutrient levels. when plants do not receive proper nutrition, just like humans, deficiencies begin, allowing disease and opportunistic organisms to take hold. the soil should be a rich dark colour, like coffee, not grey. good luck.
The white patches along the veins on the zucchini are not a problem. It's a natural trait for some summer squash and shows up more on older leaves. The yellow spots on the right might be the beginning of downy mildew. Doesn't quite look like the images here: http://www.omafra.gov.on.ca/english/crops/facts/09-013w.htm
