Downy mildew, something else, or both?

[rainbowgardener]

Neem oil comes from the neem tree, which is native to India and widely grown in the tropics and subtropical areas.

[!potatoes!]

So, the whitey spots are likely to be grasshoppers... Hmmm

note: the spot are likely to be leafhoppers, not grasshoppers. very different insects with very similar common names.

[PhillyGardener]

OK, now I'm fairly certain I really *do* have downy mildew or some other kind of fungus. I let my guard down for a week and didn't spray with neem oil because everything looked good--and also because it was raining almost every day for a little while. This morning I noticed discolored leaves on one of my 7 cucumber plants. All of the older leaves look dappled like this, but so far no other symptoms. The spots don't have sharp edges like other photos of downy mildew I've seen. (The small holes/tears are from a hail storm.) You can see two healthy leaves from neighboring plants compared with the sick looking one. Any ideas?

[img]https://i356.photobucket.com/albums/oo9/abnormalsanon2/2012-06-10114155.jpg[/img]

[applestar]

You keep saying downy mildew, but downy mildew s a more serious fungal disease and I tend to think powdery mildew before downy. Not even sure if I would recognize downy mildew.

Anyway, I like spraying with milk and water. 10~25% I,m too cheap to mix it any stronger. Usually old or leftover milk. And some lquid from cultured product -- yogurt, sour cream, cottage cheese, etc. The spray encourages lactobacillus colonies on foliage surface that competes with pathogenic fungi and acts as preventive. Bacteria stick to the leaf surfaces on their own so they are not easily washed off by rain, unlike non-biolgoical sprays -- another plus.

Those marks could also be from sucking insects underneath the leaves.

[rainbowgardener]

It's not looking like powdery mildew to me, because it doesn't have that distinctive gray powdery appearance. I'm not so familiar with downy mildew, but it isn't really looking like that to me either, still. Sucking insects sounds like a good theory.

Downy mildew is virulent. Since you first wrote in about this May 23, I'm thinking if you really had downy mildew, your plants would be clearly dying by now.

[PhillyGardener]

Well, a similar discoloration is spreading to one of my zucchini plants--that one might be powdery mildew, I'm not sure. The cucumber plant continues to look dappled and the leaves are starting to look slightly curled. All of the other 7 cucumber plants (including 3 more of the same variety) remain just fine, so while I know I have some leafhoppers and thrips hanging around and see some minor damage from them, it seems weird that just this one cucumber plant would react so poorly. At any rate, I agree it's not downy mildew--I didn't know when I first posted here that it's so rare. I do think it may be some kind of mildew or fungal disease though. I sprayed Neem on Wednesday morning and will spray milk this weekend. I don't drink cow's milk and don't keep it on hand, or I would have already

Thanks for the replies and suggestions!

[rainbowgardener]

Applestar suggested damage from sucking insects. You say you have leafhoppers and thrips. Here's one image of what leafhopper damage can look like:

[img]https://utahpests.usu.edu/admin/images/uploads/UtahPests/small-fruit-advisory/2008/08-01/grape-leafhopper-damage.jpg[/img]

Here's a similar image of thrip damage:

[img]https://www.ipm.msu.edu/perennials/images/ThripsDamage.jpg[/img]