Native Plum Mummies
Last year my native plum set loads of fruit. They grew as expected until about the size of a small green olive. Then they started to get some strange growth, exaggerated, and not even. Made me think of giganticism in humans. After which they turned gray and weight wise felt like they were made of styrofoam. This happened to every single one. What happened? and Can I prevent it? Sorry that I can't locate my picture.
Barry County Michigan fruit trees
Native plum trees are prone to a disease called plum pockets. This is a fungal diseases, somewhat similar to one on peaches called peach leaf curl. There is a fairly good summary about this disease at the following University of Minnesota web site
It is a sporadic disease that shows up on the susceptible plum varieties when certain weather conditions (mild temperatures, extended wet periods, with more than a drizzle of rain) occur in the springtime. This disease is particularly a problem in the pacific northwest where these weather conditions are common in the spring. If these conditions do not occur, then no plum pockets. A copper spray in the fall after approximately 50% leaf drop or in the spring before bud break helps to manage this disease. We have already had bud break in plum and at least one weather event conducive to infection in the lower region of the lower Michigan, so a copper treatment applied now will likely not be completely effective in preventing symptoms.
Thank you. It is good to know what I am dealing with. It was a surprise to see "all" the plums go this way last year. Now I can begin controlling it.