The plum tree is a deciduous stone fruit tree that thrives in well-drained, nutrient rich soils. This China native produces broad, rich-green foliage and blooms pink and white flowers. The fruit is a rich-colored, juicy stone fruit. This showy fruit tree can reach heights if up to 30 feet and is moderately cold hardy. The plum tree is susceptible to several diseases which, if left untreated, can be permanently damaging to the tree.
Bacterial spot is a common disease among plum trees and other stone fruit trees. This bacterial disease, like many fungal diseases, lies dormant on trees and defoliated debris during the winter months. The bacteria are then transported, by rain and wind, onto the tissue of the tree to begin infection. Infected areas of the plum tree will develop small, water-soaked lesions on its leaves, which will blacken as the disease progresses. The foliage of the infected plum tree will begin to yellow and defoliate. Trees will produce small, black, unusable fruit. Plum trees that enter multiple growing seasons with the infection will experience twig and branch dieback, branch breakage and trunk cankers. Though bacterial spray treatments can assist in reducing symptoms, there are no treatments that can eliminate the disease. Infected areas should be removed from the tree.
Black knot is a fungal disease that is common among stone fruits. This disease is transported through microscopic fungal spores that are most active during periods of wet weather and moist soils. Black knot infects the woody areas of the plum tree. Infected areas will develop wart-like swellings that blacken and harden with age. Though twigs and branches may be severely infected, the foliage of the tree will seldom show symptoms. Infected areas should be pruned from the tree using sharp, sterile shears that are sterilized between each cut. Planting resistant variations is the best defense against root rot.
Plum pocket is a fungal disease that is very similar to peach leaf curl. The fungi that causes plum pocket lies dormant on bark crevices and releases during the cool, wet periods of spring. Transported by spores, the disease infects the fruit and foliage of the plum tree. Infected fruit will develop small, white spots that coalesce, eventually covering the fruit in its entirety. Infected plum tree foliage will become deformed and eventually die. Plum pocket is controlled with a fungicidal spray designed specifically for this type of fungal disease. Infected areas must also be pruned from the tree.