Cucumber leaves turn yellow, then brown, then dead

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crabbygardener Durham, NC Sep 13, 2013

Is it normal for cucumber leaves to start to yellow in spots, turn brown in the same spots, and then shrivel and die off? (See the photos, but note that they are in the reverse order for some reason.) They did this last year, too, but they still kept growing vigorously (as they do now). Is this just a part of the natural aging process, or is there a pathogen at work? Note that nearby tomato plants have early blight (Alternaria), but I don't think that affects cucumbers (please correct me if I am wrong!). The fruits are unaffected (other than by worms that keep getting in), although sometimes they turn yellow (they're supposed to be dark green Burpless).

Thanks!

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drobarr Hummelstown, PA(Zone 6b) Sep 13, 2013

that is downy mildew on your cucumbers. If you look at the underside of the leaves you may or may not see sporilation....or a whitish or in some cases a blackish fuzz that corresponds with the yellow and necrotic spots above.

It is possible for cucumbers to get Alternaria leaf spot but it doesnt look like downy.http://web.aces.uiuc.edu/vista/pdf_pubs/918.PDF

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crabbygardener Durham, NC Sep 15, 2013

Thanks for the information, drobarr! I'll keep my eyes open earlier next year and maybe it won't hit my cukes so hard.

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JoParrott Richland, WA(Zone 7b) Sep 15, 2013

I have that on some cukes that I planted close to my wood privacy fence- the air can't circulate enough there- I sprayed with Neem oil but I think they are gone.

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drobarr Hummelstown, PA(Zone 6b) Sep 15, 2013

wet foliage and cool nights is what this oomycete fungal disease loves

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