First of all, never water in the late afternoon, as leaves don't get dry and you get mildew. Can't remember the fungicide we used last year, but your local nursery will know.

Cheri

Here's what you do if you like to be frugal: take the kid's leftover milk at the end of the meal, or milk that has gone bad. Dilute it 50:50 with water and spray on the leaves. You can break off the worst leaves. Do this after every rain. It works.
If you don't like to be frugal: buy the milk fresh and use.

IF you really don't like to be frugal: buy expensive anti fungal products.

I've been recently told a table spoon of baking soda in a litre of water can be used as a spray for mildew on squash plants. Haven't tried it yet myself, but have just started to notice some mildew spots on some of the leaves here, too. I didn't know about the water on leaves problem - I think that's what can contribute to the flowers falling off before the fruit can set, too...

Peace,
- Faerie

There was a thread on the veegie forum that talkied about milk, and it seemed to work for them. Do a search over there, and see if it pops up...and I certainly don't spend a fortune, lol, could not afford to.

Cheri

I just found a site that says it's NOT water on the leaves that causes this. It says:

Powdery mildew is a fungus that grows well in arid climates, such as Colorado's. It can occur on almost any plant including flowering plants, grasses, vegetables such as squash and cucumbers, trees, shrubs and even weeds. Fruit production on these plants may decrease slightly if powdery mildew is present.

Several weather or environmental conditions favor powdery mildew disease. Unlike most plant pathogenic fungi, the fungi that cause powdery mildew do not need water on leaves to infect the plant. It does, however, need relatively high air humidity. That's why the disease is common in crowded plantings where air circulation is poor and in damp, shaded areas. Young succulent growth usually is more susceptible than older plant tissues.

Several practices will reduce or prevent powdery mildews. Before purchasing a plant, ask if it is powdery mildew resistant. If resistant varieties aren't available, avoid planting in low, shady locations.

Once the disease becomes a problem:

Powdery mildew is not always easy to control, but you can do several things to manage the disease.

Avoid overhead watering to reduce relative humidity.

Clean up and dispose of all leaves and vegetable debris that falls to the ground in autumn.

Increase air circulation. If plantings are dense, selectively prune to open the area up and reduce relative humidity.

Consider using a fungicide labeled for powdery mildew, but use in conjunction with the above-described practices. Follow exactly instructions on fungicide label. Several "alternative" pesticides work well to help prevent the disease. Sulfur dusts and horticultural spray oils are two non-toxic, effective alternatives that will protect uninfected leaves from the fungus. (Be sure to follow label directions; sulfur can burn leaves if used when the air temperature is above 90 F.) Synthetic fungicides such as Daconil 2787, Maneb and Zineb also can be used to protect foliage from getting this disease.

None of these products have great eradicative properties. So don't expect to take a severely infected plant, spray it and find that all mildew disappears. The products are meant to protect leaves from infection rather than to eradicate infections.

Here is a link that might be useful: Colorado State University Cooperative Extension

I am using neem oil for the first time this year and am very pleased with the way it's performing. First, as opposed to the milk solution, you only have to spray once every 12-14 days. It seems to put the disease at an abrupt halt.

Buy yourself a big container and mix it up yourself for the sprayer.

Cher

I have tried the neem oil also on the butternut and it does seem to arrest the mildew, though not completely eliminate it. And don't give up. I thought I had lost the summer squash plants but just kept cutting off the bad leaves, mulching with seaweed and good cow compost and suddenly the plants are looking much healthier and starting to produce again. Also, it's finally been hot here in New England for a week or so.

Mildew is always a problem in the fall for me, I try to keep ahead of it by cutting off the leaves as soon as they look funky. Baking soda does work, won't fix infected leaves but can stop the spread. I have used copper fungicide listed for organics with sucess. I also cut back my watermelons when they got mildew and they grew back clean. Keep squash and melon leaves dry.