It's not fatal unless all the leaves are falling off. If it's just the oldest leaves it's little concern. If it's all the leaves then you may need to spray a fungicide next yr.

Thanks very much, fruitnut, for your answer. I should have mentioned that these particular cherries are all new this year and came by mail from several nurseries. It's definitely older leaves, though. Leaves at the tips of the branches are fine. I should have started regular spraying with neem as soon as they leafed out. Next year, for sure. For insects, I'm using diatomaceous earth. I'll start spraying neem now to, hopefully, prevent fungal infection of other plants

Do you think DE is effective enough against bugs to be worth using? I like it because it doesn't hurt anything else (I wrap a t-shirt around mouth and nose while applying).

Cherry trees have various problems which vary according to the region they are growing in.

3 affected leaves don't tell/show us what the entire tree is doing.

Please post images of the affected trees so that we reasonable chance to offer a reliable judgement re their overall condition.

Thank you, I will.. (Probably the pics being out of focus doesn't help, either. I shake a little.)

Fruitnut -- Surround and DE are different. Cut and pasted from the site of the company that produces it, NovaSource:

"Surround protects plants in three ways promoting higher yields and the harvest of
more marketable fruits and vegetables. First, the calcined kaolin
particle film of SURROUND protects fruit against direct sunburn and heat
stress damage. SURROUND can reduce sunburn losses by up to 50%. Second,
SURROUND keeps plant canopies cooler, which leads to more efficient
photosynthesis and higher yields in high light and heat environments.
Lastly, carefully timed treatments of SURROUND reduces the activity of
certain insect pests, delaying or even eliminating the need to apply
conventional insecticides. Certain insects that vector harmful diseases
such as the Asian Citrus Psyllid that carries Citrus Greening
(Huanglongbing or HLB) are inhibited from feeding (and spreading HLB) by
the presence of Surround on leaf surfaces."

DE is not clay at all. It's the shells of tiny, ancient sea creatures. I haven't read about any protection against sunlight. Apparently, it cuts up the bugs and sucks the life out them. That's all. I didn't use DE for a long time because the applicators I found didn't appeal to me. Then I found this Duster Applicator Hand Crank 1.5lb Hopper at Amazobn:

https://www.amazon.com/Duster-Applicator-Crank-1-5lb-Hopper/dp/B0037LTK7S/ref=sr_1_60?s=lawn-garden&ie=UTF8&qid=1499953322&sr=1-60&keywords=applicator

I was impressed by the demo at YouTube so I bought it. I love it. Worth every penny. Covers everything evenly and FAST. Some reviewers complained that it's too expensive for such lightweight plastic, but if it were heavier, very few gardeners would be able to use it. I used it all last summer and this, and it hasn't broken yet. Probably not a good idea to drop it on your stone patio.

Bernard

It looks like cherry leafspot to me. I have 2 tart cherry varieties. One of the two is far more prone to leafspot than the other. Some years I do not get it and sometimes I do. One year it was so bad both my cherry trees were 100% defoliated by mid August.

So far I found a few leaves with leaf spot while picking cherries (harvest will be done in a few more days). If it gets worse I will spray with chlorothalonil to prevent the spread of this foliar issue.

Thank you, spartanapples. I'm sure you're right; it is cherry leaf spot. The pictures match up too well for it to be anything else. No harvest for me this year. My more mature trees fell victim to voles last winter -- that won't happen again. Some of my living cherry trees will be mature enough for their first crop next summer. I have about 20 tart cherries of different varieties (in containers). Only about 5 of them show the fungus. So I should spray chlorothalonil now, yes?

Chlorothalonil can be sprayed on cherries in spring (white bud stage) up to shuck split stage then illegal to spray after that until all the fruit is harvested. Since you have no fruit, I would spray now as a preventative measure so the fungus doesn't spread to new leaves.

It is amazing how fast cherry leaf spot spreads this time of year if the conditions are right. One week just a few leaves infected and a few weeks later the tree is covered with it. If you have the chloro I would suggest treating.

20 cherry trees? Wow, you must eat a lot of cherries. I get around 20-30 quarts (after pitting) from my two trees which I split with my brother-in-law. I have a Mesabi and a Surecrop. Years ago I had a North Star and one year that North Star yielded 26 quarts (after pitting).

What varieties are you growing?

Try myclobutanil instead. The common brand at Home Depot or Lowe is Immunox.

hello, spartanapples --

I have 1 each of Montmorency, Balaton, Jubileum, Romeo, Juliet, Danube, Lutowka, Almaden Duke, Pie Cherry (which is the no-name name Hidden Valley Nursery gave to a neighbor's highly productive tree). I have 2 or three of each of these: Crimson Passion, Carmine Jewel, and Bali Evans. That could only be 15 at the most. Oops. I don't keep close count because I also have a bunch of figs, 6 hardy kiwis, 6 Siberian kiwis, a couple pears, 2 peaches, 2 rhubarbs, 1 seedless che, and 3 persimmons. I think that's about it.

Except for 7 paw paws in the ground, they are ALL in containers. None will get very big. Long story short, I do containers because my soil is wall to wall clay, except for the area dedicated to paw paw. The clay could be amended, but it would take too long. I'm too old for such a long-term project.

Just as I was about to give up on the whole thing, I discovered the container gardening forum. I studied the principles that are beautifully outlined (thank you forever, Al Tapla), applied them, and I love the whole process. For me, much more fun than gardening in the ground. I can have a far greater variety of plants, I can understand and control their progress much more closely, and if something doesn't work out, I've got plenty more that are doing great. Also, I had the fun of designing and continuing to build planter boxes.

I don't have a good pic that shows everything. Right now, everything's a jumble, but here's a sample.

Bernard