I grow a couple of different kinds of plums and they all should be sprayed (sometimes I do, sometimes I don't). They are easy trees to grow but hard to get good fruit from. This area has a lot of plum eating bugs. If the branches are wimpy you should thin the fruit so that it doesn't break the branch and damage the tree. A lot of the time the buggy fruit will end up falling off on its own and you don't have to do much work. Birds and squirrels will also eat the fruit - often before it is ripe.

Thanks so much for your response, John! I really appreciate it!