Cherry leaf spot - help please

Greetings.
My Northstar Cherry has produced less and less poor quality fruit the past three years. This season it showed clear signs of cherry leaf spot: yellowing, dark spots turning to holes, significant defoliation. Do we have any options for planet-friendly treatment? Will the tree recover and produce again, or should we just call it a day, remove it and start over with something else?
Thank you.

Don't throw in the towel yet. Your tree is likely sick because it can't fight off disease on its own, because the soil it's in is sick and depleted. Here is the best option, and it's very planet friendly- Get a soil test done, the kind you send off to a lab. You may wonder which lab, well there are many good labs out there, I happen to use Logan Labs. With your soil test results, you will know which minerals are deficient and if the pH of the soil needs adjusting. By correcting the soil pH and replenishing the depleted minerals, the soil microbial life will begin to flourish, which in turn will make the tree begin to thrive. Adding compost to the soil and mulching the soil are two more easy and beneficial steps you can take also. With healthy living soil, the trees immune system will begin to function efficiently and your cherry tree will be able to fend off disease and infections. The tree will also begin to bear more and more of a higher quality fruit as the years go by.

If you choose to get a soil test done and find the test results confusing or difficult to interpret, just PM me I am happy to help to you interpret your soil analysis.

Cherry leaf spot is caused by the fungus Blumeriella jaapii, so a soil test is not going to do much for eliminating the fungus, it will however allow you to build the soil minerals to enable the tree to resist the fungus in future years.
There are some bacteria and other fungi that will be of great benefit to this endeavor, this means brewing some compost teas and applying them monthly to build up the numbers of these beneficial microorganisms.

The first thing to do when dealing with any fungal infection is to remove all infected materials (leaves both on the tree and on the ground, any twigs that show signs of fungal invasion, etc.).
The second thing to do is spread an anti-fungal on the soil to help prevent any of the fungus that is in the soil from being able to survive.
There are several very good, organic fungicides to choose from and there should be one that will work best for your location and situation, your local extension service should be able to make an organic recommendation.
This link should be of help to you. disease control for cherry orchards

Know thy enemy well and you can overcome it in a natural and organic way that does no harm to the earth mother.

Redhawk

Thank you both for responding. I should have included site info... Northern Michigan, growing zone 4B, sand rather than soil (that is a work in progress). We have not done a soil test; it is on the list. I will continue work on building soil health. As soon as I noticed the signs I began removing diseased leaves. One observation: the worst-hit branches were those upon which I observed ants farming aphids. Is there any connection between cherry leaf spot and aphid/ant activity?

aphids suck sap (tree blood) and this helps to weaken the tree.

When a tree has been weakened enough, it can not fend off infections, which can come from critters (bugs, etc., fungi, viruses).

Good mineral content bolstered by good humus, bacterial, fungal, and the other necessary microorganisms that create healthy soil are the best preventative and also the best cure for such infections.

Aphids don't actually bring the infection but they make the tree more susceptible to it because of the new bleeding wounds.  The harvester ants are more likely to be the ones bringing any infectious material into the tree, they do the most traveling.

I follow a rake and burn regimen in our orchard, this helps keep any infectious materials from building up. I also cultivate lady bugs by providing over-wintering habitat for them.

Redhawk

Gotcha, brilliant - thanks!