Stemy:

The roots of cherry trees are very sensitive to poor drainage or excess soil moisture. You don't say whether the area beneath the trees has received a whole lot of rainfall, or if you are watering them in addition to natural precipitation. Problems in the leaves are often a reflection of problems in the roots, and I suspect that is what is happening here.

Right next to a foundation is not the place to plant cherry trees, even if they are full dwarfs. Worse still if these are standard root trees.

Don Yellman, Great Falls, VA

Thanks Don. We have rec'd a good amount of rainfall this summer (and a few heavy rains recently), so it's possible that the water is making them uncomfortable. I was providing supplemental watering in the spring and early summer, but not much since. I've been out of town a lot over the last few weeks, so my wife has been handling the manual watering duties on some of our other plants. It's certainly possible that she was watering the trees while she was watering some other plants in that area. I need to check with her and find out.

Interestingly, the one of the three that is not experiencing the leaf curling has some other plants (watermelons) in the ground all around it. Those plants have been receiving (some) supplemental watering, but I guess that they are probably helping to dry out the area around non-curling tree.

The picture makes it appear as though the tree is planted closer to the house than it actually is planted. They are still a bit close (5 feet from foundation), but since they are full dwarf, I thought I'd give them a try. Time will tell whether or not they like their placement :)

If this is a drainage/excess water issue, are there any recommended actions besides letting it dry out a bit more and limiting supplemental watering?

No, Stemy, the only answer to excess water is either better drainage or less water or both. A dry cherry tree is usually a happy cherry tree.

Don Yellman, Great Falls, VA

Looks like powdery mildew to me.

Hmmm... actually, I think that you both might have a point. I checked the moisture in the soil and it was significantly higher on the two with curling leafs. I think that I need to try to make a downspout adjustment to help divert water away when it rains.

In addition, since I took the pictures above, the white-gray has spread to more leaves. Should a spray of Neem adequtely address the mildew?

Stemy:

Powdery mildew will preferentially attack weakened leaves, in this case by excess moisture. I have not found neem to be effective against anything, fungal or insecticidal. I think neem is basically a scam. Sulfur may be effective against powdery mildew, but it is best as a preventative, not a cure. The best assistance you can offer your cherry trees is to dry them out.

Diverting the downspout is a really good idea.

Don Yellman, Great Falls, VA

Don,

Don't you think the following antifungals might work? Of course drying out the tree is important.

Chlorothalonil can be applied until shuck fall on all stone fruit; it can provide season-long control with one spray.

Myclobutanil

strobilurin (azoxystrobin Heritage upwardly mobile in plant, trifloxystrobin Compass mesostemic moves to other side of leaf, pyraclostrobin Insignia mesostemic)

JMS stylet oil (apply early, once or twice, foliar toxic)

I don't disagree that water and powdery mildew may be affecting the trees, however when I look at the pictures the mottling and billowing looks very suspiciously of a viral disease. Are the leaves also showing signs of thickening? Many plants are subject to mosaic viruses and once infected there is no cure other than replacement. It is usually spread by insects sucking sap from an infected tree and going to one that isn't.

At this point, try to address the water issues and watch the mildew, then wait for next year to see if they develop the same mottling pattern. If your trees are infected by a virus, they likely had it when you bought them and should be replaced to avoid insects spreading the disease to other trees in the area.

JELLYMAN:
I strongly disagree with your comment about neem oil!
I have used it many times with excellent results. One example is my usually healthy miniature rose that had aphids, spidermites, and columbine sawfly worms all at once this year. I applied neem oil to the entire plant to the point of runoff. (Neem oil will not be effective unless you spray BOTH the UNDERSIDES AND TOPS of ALL leaves.) Within a day or two I saw a drastic reduction in visible pest populations. The rose recovered with just the one treatment. The following are excerpts from www.discoverneem.com/neem-oil-insecticide.html :

"Neem oil does work, but the way it works is different from other insecticides. Neem is not an instant, knock down, kill everything pesticide."

"Neem oil has many complex active ingredients. Rather than being simple poisons, those ingredients are similar to the hormones that insects produce. Insects take up the neem oil ingredients just like natural hormones."

"Neem enters the system and blocks the real hormones from working properly. Insects "forget" to eat, to mate, or they stop laying eggs. Some forget that they can fly. If eggs are produced they don't hatch, or the larvae don't moult."

"But this is not something that happens over night. People spray neem oil as insecticide, and expect everything to die instantly, because that's what they are used to from chemical poisons. When that does not happen they conclude neem insecticide does not work."

"The subtlety of the hormonal effects, and the fact that they may take days or weeks to manifest, makes people overlook them. Ill informed gardeners seek instant gratification, i.e. lots of dead insects immediately, rather than a balanced environment in the long run."

Read more: http://www.discoverneem.com/neem-oil-insecticide.html
I would advise anyone seeking advice on this forum to try remedies for themselves. As a well educated and informed gardner, I know that first hand experience is the best way to make up your mind. So don't take my word for it, try neem and other safer insecticides yourself before you use toxic chemicals that are poisoning our earth.

Angelica,

Don is an experienced fruit grower, not a rose gardener. That background is important because major fruit tree pests are the real bane of fruit growers. Aphids and spider mites are generally (though not always) considered minor pests. Spraying both sides of the leaves to the point of run-off with a summer horticultural oil would likely provide the same control as your neem. Horticultural oil is considered very safe and some horticultural oils are organically approved.

The neem advertisement may seem to describe a novel mode of action, but it is simply describing an insect growth regulator, which has been around in synthetic form for a long time.

I'm glad you're happy neem, but should you find some serious pest pressure on your fruit trees, I think you'll find your neem won't cut the mustard.