The plum tree is a large deciduous tree that can also be grown as a shrub. With more than 200 variations, the plum tree is a perennial stone fruit tree that can grow up to thirty years. The plum tree is susceptible to several diseases which may attack the fruit of the tree as well as the trunk, branches and stems.
Plum pocket is a fungal disease that is quite common in stone fruit trees. This disease causes the infected fruit to become enlarged with hollow centers. The fruit's exterior is often thick with enlarged shoots and curled leaves. The shoots and foliage may also develop a dark, sooty appearance and premature fruit drop may occur.
Black knot is a serious and common disease of the plum tree that develops during the early spring. This fungal disease causes elongated knots on the tree's branches. Untreated black knot will kill the branches, causing growth stunt and eventual death of the tree. Cankers may also develop on the tree's branches and trunk.
Brown rot is a fungal disease that overwinters on mummy fruit that remains on or around the tree. The fungal spores are then passed onto developing shoots and fruit during the spring and summer months. This disease is common among all stone fruits. The disease initially causes small circular spots on the fruit and can cause rapid rotting thereafter. If left untreated, the disease can continue its infection passing through the fruit and into the stems and branches.
Verticillium wilt is a dangerous disease for the plum tree. Most infected trees will not survive this disease. Verticillium wilt is a soil-borne fungal disease that passes through the tree's root system and spreads internally throughout the tree. Most trees will not show a sign of infection until after the disease has damaged the tree's internal system.
Powdery mildew is a fungal disease that appears as a powdery coating on the leaves of the tree. Although the disease generally produces in the early spring, the tree usually does not show signs of infection until the end of the growing season. Though the disease initially attacks the foliage of the tree, if left untreated, powdery mildew will surpass the trees foliage to attack the stems, shoots and branches of the tree.
Plum pox is a viral disease that is common among stone fruits, especially the plum tree. This disease, unlike most plum tree diseases, is passed from tree to tree by infected aphids. This disease causes yellowing of the foliage veins and the leaves' surfaces. Severely infected plum trees will see browning and dying of the fruit with irregular formation.