Yellow spots on leaves of otherwise healthy cucumber
I have four Marketmore cucumbers. They are my favorite in all of my vegetable garden, and that's saying a lot (I planted about two dozen different vegetables). They have been fruiting awesomely (I harvest a cuke on each every day) and two of them have main vines about 8 foot long, outgrowing the trellis. The cukes are sweet, tender and crunchy.
Now, about two weeks ago, small yellow spots appeared on the leaves literally overnight (they also appeared on a neighbour's cukes the very same day). Not all leaves are affected either: the problem is concentrated on a 2.5-foot section about two feet from the roots. The yellow, or I should say buff, spots have been slowly growing. The undersides of the leaves aren't affected in any way. No fuzz to be found anywhere, so it doesn't look like any kind of mildew so far.
Since the spots appeared, nothing else has changed about the plants. They still produce delicious cukes (I harvested five yesterday) and other than the affected leaves, everything else looks healthy. The main vines are going crazy and they look like they want to reach the roof. But the little spots are growing and they will most likely take over the entire leaf and the leaf will most likely die.
What should I do? I am not necessarily interested in knowing what exactly is wrong with my cukes, just in knowing in general whether I am dealing with insect damage, bacteria, mildew, etc., and consequently, whether I should spray, chop those leaves off, etc. Oh, and I also caught a few striped cucumber beetles, and they are mostly around the cukes, even though I have melons, zucchini and pumpkins as well. But there are not many and I am quite adept at catching and crushing them.
Between the cucumber plants, I have a watermelon with two tiny melons on them, one of which has been growing like crazy. The watermelon looks nice and healthy and I want to keep it that way, so I am afraid that whatever is wrong with the cucumbers might attack the watermelon. It is my only watermelon that definitely will produce mature melons by the time cold weather sets in (I have three more that may or may not have time to ripen).
Also, I feel I should mention that all of my plants have suffered a bad hail storm about a month ago. They all have little holes and tears in a limited amount of foliage. None of them seem to mind this (some of my bush beans have a lot of holes but they are still blooming away and producing delicious pods). I wonder if the spots on the cuke leaves may just be scars from that hail storm. The spots appeared about two weeks after the hail storm.
Sorry, I can't post a pic right now as hubby has the camera today. I'll post one tomorrow, though.