Lowraine - Yes, you have reason to be concerned. What you have is powdery mildew, and it will continue to spread throughout the plant. Although it does not damage the existing fruit, it does limit the amount of photosynthesis that takes place, by destroying the plant's leaves. Remove all of the leaves that have it on them (assuming there's still some healthy leaves at the top), and spray copper fungicide on the new growth every week. Humid conditions is what the fungus thrives in, so that's why you have it. Cucumbers, cantaloupes, squash, and pumpkins all are subject to get it....

EG

Yup. PM has gotten all of my squash, zucchini, and cantaloupe. At least I can start fall items now, so I don't feel so bad about it.

Oh yuck, my squash are all infected too. There has been a lot of rain around here.

I think I may have the same problem as lowraine, ribbit32004 and floodthelast. Here is a picture of my squash. Is this powdery mildew??

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I was hoping to keep my SFG organic. Is the copper fungicide that engineeredgarden recommends considered organic?

Has anyone tried the copper fungicide and, if so, has it improved your problems?

I cut the leaves back and sprayed mine but anything I spray gets washed away by the constant storm that comes through this week. I pulled some of the squash up today.

My husband and I were only gone for 2 days, and when I went out to look at the garden this afternoon our beautiful squash plants were WHITE! I mean really white! Not even splotchy white but like a fine snow had fallen! We have never had this happen before in 25 years of growing a home garden, but have been experiencing a record-breaking heat wave this past week. I don't know if that has anything to do with this problem.
We sprayed with 1/2 and 1/2 1% milk and water solution. I wish some others would have come back and told if it worked for them, but I will come back and let you know if it worked or not. I sure hope it does!

One thing that definitely does work is 1 teaspoon of baking soda and one teaspoon of Murphy's Oil Soap mixed with a quart of water in a spray bottle, like an old Windex bottle or something. Or you can use 1 Tablespoon of each in a gallon sprayer. Spray at dusk, though, to avoid the sun cooking the plant during the day, and cover both sides of the leaves thoroughly.

Hi
If I have powdery mildew on my squash leaves and have had to cut off most of them, will my squash receive enough nourishment from the few leaves left, or should I just harvest them now?

Lily,

Are they summer or winter squash? For summer squash you should harvest them at any time. For Winter squash, you should try to leave them on the plant as long as the stem on the squash is green. That means that the squash is still being fed by the plant. When the stem turns brown, feeding has stopped so there is no reason to leave them on the vine.

Hope that helps,
Susan

Has anyone tried Neem Oil? Same rule applies with dusk application to avoid burn. I have tried it with other plants with really good results but never thought of doing it with the squash. I used a capful or less, in a spray bottle, just enough to make it 'milky'. I WILL check back in a couple of days and report any changes. I will apply tonight. Wish US luck!

Additionally, there IS this. I am lactose intolerant and so only drink coconut milk...LOL Might be worth a trip to the corner store though. Milk seems 'nicer' than Neem somehow...LOL