I saved a bunch of cucumber seeds last fall, from a variety I can only get by mail order. I planted a short row of these several weeks ago and the leaves are already damaged badly by fungus, even though they're only knee-high up a fence, I've sprayed them a couple of times with Daconil, and they haven't produced any cukes yet.
My cucumbers always get this, spotted leaves starting at the bottom, then the leaves turning brown and dying, late in their life cycle - after they've produced cukes for weeks and are about to die anyway. I've never had it happen this early, though, and I can tell this is going to kill the vines before they can produce much. My garden is clean and that row is mulched, and I'm pretty sure this is happening because there are fungus spores on the seeds I saved. I saved them very late in the season when the vines were already withered by fungus. I cut up some overripe, yellow cucumbers that were hanging on the vines and put the pieces in a bucket of water right by the dying vines in the garden. The cucumbers fermented in the bucket for a week or so (a real nasty-looking ferment as I recall), then I rinsed the seeds with water and dried and saved them. I see now that because of the way I did that, the dried seeds are probably coated with lots of fungus from last year's dying vines.
I want to plant some more of these, but I need to soak the seeds in a mild fungicide before planting. I'm thinking of using hydrogen peroxide and water, half-and-half - what do you think?
p.s. - Horseshoe, these are the Japanese Long seeds that I sent you some of. Are you having the same problem with them? If so, I'm sorry.
Thanks, RickCorey, I'll blend the peroxide as you suggest.
Paul - Downy Mildew, eh? I've never had that before, but I bet that's what it is. The worst affected leaves, especially the old remaining false leaves at the bottoms of the vines, had gray, fuzzy mildew growing on them. Regular leaves start out with yellow spots, turning to brown, turning to crispy dead leaves.
I just trimmed off all the affected leaves I could find and sprayed the vines with Daconil (Bonide Fung-Onil). Downy Mildew is listed on the label among the fungi this product treats, and the instructions say to spray cucumber vines every 7 days. I already use it that way on tomatoes.
I'm pretty sure this fungus was carried on the seeds I saved, as I have two varieties of cukes planted next to each other along the same 16' fence. Only the vines grown from seeds I saved are showing this infection. The other cucumber vines grown from store-bought seeds aren't affected yet but I sprayed those also.