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I have some butternut squash plants which were doing fine until recently. Their old leaves have been turning yellow, then brown and shriveled, and finally die. Now, many of the leaves (including the newer ones) have gray powdery blotches (maybe mold?) on them and there are tiny moths by the plants. When I rustle the leaves, a whole bunch of these moths get disturbed, fly into the air, and land around another squash leaf. I live in northeast Florida. Pictures of all the problems, including a small photo of one of the moths on a screen, are included.
Does anyone know why the older leaves are dying, if the gray blotches and moths are harming the plants, or of a solution to these problems?
You have powdery mildew. Try http://gardensalive.com for organic solutions. A horticultural spray oil, like neem, is probably your best and safest bet to treat the stuff. The fungicides can be toxic and I'm told that there's resistance building up, so they don't even work as well, but if you try a fungicide make sure it's safe for edible plants and that it's specific to powdery mildew.
Violet, I am no expert, but I believe it's natural for some of the first/older leaves to die off. All my veggies and herbs have that habit, but they are all doing well.
I can't speak to your mildew prob, but I wouldn't worry about the older leaves dying. I do see in the bottom pic that more are turning yellow. The ground looks dry. Is it?
Now it's hot and sunny, and the leaves are wilting (they usually do temporarily when it's sunny, but water or cooler temperatures revive them), but the soil is still kind of moist. Does insufficient water cause squash leaves to turn yellow? How much water do they need? These are in full sun and endure summer temps. in the 80s and 90s. Do they need more shade?
No, they love sun. I suspect that those "moths" if in large numbers are doing a number on your plants. I don't have anything like that, but the subtropics have lots of pests that don't make it this far. Sucking insects not only bleed a plant dry, but transmit viral diseases.
I recommend a Rotenone/Pyrethrum mixture to handle garden pests. Rotenone is an old organic pesticide and Pyrethrum is a newer one. Some folks no longer consider rotenone organic (although it's a plant extract) because it can kill fish if it gets into the water in sufficient concetrations (not likely given the amount the home gardener would be using, plus it breaks down in about 3 to 5 days). Just don't use it near a pond.
Google Rotenone Pyrethrum for several potential suppliers. GardensAlive carries it but it's expensive there. Several other suppliers carry it but I don't know anything about them so can't recommend for or against.
One thing, if you get a catalog from GardensAlive for the first time, you can get up to $25 off your first purchase (excluding shipping).