Question
When the fruit is well formed , a scale appears on some fruit, also a drop, or two, of gelatinous liquid forms at the bottom of some fruit. But worst of all, as the fruit grows larger it turns a dark blue colour, shrivels and rots
Last year all the fruit the fruit rotted, and this year it appears to be the same.
WHAT CAN I DO TO STOP THIS BLIGHT?
Also how should I feed these trees?
Thank you in advance for your answer

Answer
Richard:
The liquid may indicate a boring type of insect such as the Plum Curculio.  Google this critter and read about it and look at some of the pics to compare.  I am assuming you are also referring to scale insect being on the fruit too.  Several insecticides such as dormant oil. can be effective. Do not spray this on the tree when temperatures are over 80F. Check in with one of your better garden centers in your area for some suggestions for these bugs.

The fruit rot may be called brown rot, a fungus disease that rots the fruit right on the tree.  It gets mushy, covered with a gray "fuzz", then shrivels to a big ole raisin!  Proper pruning before springtime to remove any dying branches, pickup any rotted fruit on the ground. Several fungicides labelled for this disease. Timing of the spray is important. Check with your local county Extension office for that info. These folks usually can help out a bunch and help you get your problems properly ID'd and suggest management strategies.

Regards
STeve