Plum pockets Photo: Chad Behrendt

Plum pockets, a disease caused by the fungus Taphrina communis, occurs on wild and cultivated plums. However, plum pockets is rarely considered a serious threat or economically important.

Symptoms first appear as small, white blisters on immature fruit. These blisters enlarge as the fruit develops and soon encompass the entire fruit. Infected fruit becomes abnormally large (3-4 times its normal size), misshapen, and bladder- like with a thick, spongy flesh. The plum seed does not develop, so a hollow pocket forms in the center of the fruit. Infected fruit is initially red colored but later appears gray as it is covered with a powdery fungal growth. Eventually, infected fruit withers and falls from the tree.

Infected fruit produces spores, which can infect healthy fruit and survive winter on healthy twigs and buds. Removal of infected fruit will help reduce the number of these spores. If infection has been severe in past years, plum pockets may be controlled by a single spray of lime sulfur or Bordeaux mixture applied before the buds swell in early spring.