Pronounced White spots and powdery white spots are two different things. Powder mildew is the latter. They are usually small spots at first and gradually can cover all of the leaf. I am dealing with powder mildew on my cukes right now. It will not disappear with just one shot treatment. I spray with neem oil solution. It will kill them first time or second for sure. But then you will find other places. Spray them with hand sprayer, such that the entire leaf is almost washed with it. The next day they will be clear of all mildew. Keep checkin, keep spraying. The good thing about NEEM OIL is that it will not harm the leaves. So you can spray as often as needed. But with chemicals you cannot do that. Last year I almost lost my gourds, even I sprayed them (per instructios)with chemicals that claimed to kill powder mildew. There is another home made spray that I have not tested its effecticeness. Formula: -- 3 parts chlorine free water(chlorine can kill the bacteria in milk, that is needed) --- 1 part milk (I would use low fat. The oil can also be a barrier) --- 2 teaspoon of baking power per gallon of mixture. It has been said that the bacterial action of baking power in the milk is responsible for destroying the fungi. Therefor, I would make fresh batches every time.

You can use Neem oil to help control it. It's organic, and it won't hurt you any if you get some of it on your zucchini. You'll want to apply it right before dusk as to avoid spraying it on active pollinators (as well as to avoid damage from the sun amplified by the oil in mid day). It should dry by morning. You'll need to reapply every week or two depending on the severity of the problem (Be sure to spray underneath the leaves as well. There's usually more on the bottom of the leaves than there is on the top. Also spray the stems and main vine.) Powdery Mildew propagates due to warm and moist conditions. This post was edited by Sromkie on Tue, Jul 2, 13 at 20:39

This is my first year garden too, and my summer squash had the same spots, but they were on the leaves. I couldn't see down to the bottom because realized too late that I'd planted too thickly. Initially, I tried cutting off each leaf that had the powdery white spots. That slowed down the speed of the spreading, but it would still spread. I was careful to wash all my garden tools as well to prevent spreading the fungus, and I also watered from a soaker hose, never on top. I thought because it had been so hot, fungus wouldn't be a problem, but it was! I was chopping off so many powdery mildew leaved, I was afraid it would inhibit production. So, off I went to the store to pick up some Daconil. So far, I've done three applications, and everything looks MUCH better. However, I still see lingering signs of powdery mildew trying to rear it's ugly head. Try treating with a fungicide. Powdery Mildew spreads SO, so quickly. Good luck to you. And, if it's not powdery mildew, then I don't know what it is.

Thanks for the reply! Yes, I can afford to replace it. In hindsight, I think it was more than simply the ill-timed transplanting that killed it (although that hurt it, no question), but I'm thinking that in addition that particular location isn't very white pine friendly. The spot is "wetter" than I anticipated. So it was probably a combination of the summer transplant and waterlogged roots. The pine in question has many, many branches that are browned all the way out to the tips. If it's a goner, maybe a bald cypress would do better there? I'll see if I can get a pic of the tree.