What disease is ruining my fruit trees
Thanks for the pictures. Not sure about the lack of fruit. Did the trees bloom? Was there a freeze before or after bloom which could have killed the blossoms and the fruit. Were there bees to pollinate the bloom or was bloom cold and windy. The black growths are from black knot a disease that attacks plums and cherries. Here is are some links to the disease and some controls.
If it is not too bad you can cut it out but if there are lots of black knots on the trees you will be cutting hard for several years.
The picture of the apple leaves makes me think you had a real problem with apple scab. http://www.ipm.msu.edu/diseases/apple_scab
If you do not spray your trees with fungicides the scab fungus can cause them to lose their leaves early and look pretty ratty. Controlling apple scab requires fungicide sprays to protect the leaves and fruit from when the leaves first appear until about a month after bloom. If you have no scab at that time you can stop. If you still have apple scab you need to continue to spray to control the disease. Here is a link to an article on apple scab control for home owners posted by the University of Minnesota.
There are other home fruit pages posted there.
I don't know what your problem with pears is but it could be pear scab which is similar to apple scab.