Question
I have a 15 year old self pollinating grafted sweet Duke cherry tree trained against a south facing wall in a narrow border and grassed in front.
Despite spraying the tree with tar oil in winter and a proprietory bug killer in spring, in recent years it has suffered particularly from black fly on the tips of the fresh growth. I have resorted to picking out the infested shoots.
More depressingly however, is the fact that although it appeared that I was set for a bumper crop this year, nearly all the fruit has been blighted by some form of disease that prevents the fruit from maturing and instead turns it reddish brown before shrivelling and dropping off. I don't think this is the common 'Brown Rot'.
I have tried picking out all affected fruit to attempt to salvage a percentage of the crop, but I fear that I shall lose the lot this year.
I would appreciate any advise concerning preventative measures I should employ in future that I might enjoy more of this delightful fruit?

Answer
You have a bacterial infection in the phloem and or xylem of your tree.  This is causing the sucrose levels to drop.  This will also cause a buildup of amino acids especially after a fertilization as the tree cant synthesize proteins fast enough.  

Putting oils and pesticides on your tree is only a bandaid and will do nothing for the nutritional balance your tree is requiring.

You need to get things moving and get your sucrose levels up.  When you do this you will get nutrient flow back out to the ends of the limbs and your fruit will be normal and your insect problems will go away naturally.  

There is only one product that I know of that does this.  

go to atomicgrow.net

It will be very expensive to order this but it is the only product that will systemically flush your problems away solving all of your problems and actually very quickly.  You may even get another flush of fruit this season.

Good Luck

James