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Plum Tree Leaf Disease

By Sheri Engstrom ; Updated September 21, 2017
The  Plum Tree.
Plum tree image by Stana from Fotolia.com

The plum tree is considered a stone fruit from the genus Prunus. This includes a large group of deciduous and evergreen trees and shrubs. They are well liked for their beautiful spring blooms, colorful leaves and the sweet fruits with a hard pit that some varieties produce. However, they are also prone to leaf diseases.


The flowering purple plum tree.
A´rboles en flor image by otero from Fotolia.com

There are many hybrids and varieties of plum trees including ornamental flowering plum trees. Examples include the purple leaf plum tree, the Japanese flowering plum tree, and the white flowering plum tree. Some of these trees are native and some have been introduced over time. Many of the varieties were bred to develop high quantities and better-quality fruit, while others were bred for beauty, abundant blossoms or survival in different climates.


Plums from a fruit tree.
plums image by dinostock from Fotolia.com

The many varieties of ornamental plum trees are easy to care for and easy to grow. They do best in well-drained, slightly acidic soil with a pH balance between 3 and 6. This ensures good flowering and fruit production. Sunny or partial shade locations are best for plum trees. Young trees need more water than established ones. Fertilize before blooming and diminish after it has produced fruit and gone dormant.


Pruning helps the tree grow healthy.
sécateur de jardin image by YvesBonnet from Fotolia.com

Plum trees are pruned to maintain or improve tree structure, vigor and the lifespan of the tree. Prune plum trees right after flowering to promote better health. Prune trees for size control in the winter. Pruning can reduce defects or structural problems in the tree. Diseased or dead branches are removed to prevent fungi from infecting other parts of the tree. Remove live branches if necessary to allow for increased sunlight and air circulation within the canopy. This aids in the reduction of certain diseases.


Verticillium wilt causes the leaves to lighten and appear dull in the early summer. The leaves start dropping without wilting at the base of the infected branches. It can infect only one side of a tree or an entire tree. The fungus enters from the roots. Bacterial spot and shot hole fungus are similar in symptoms but caused by different bacteria. These diseases are most noticeable on the leaves even though fruit and young shoots also become infected. The bacteria can cause leaf spots that look like water-soaked spots on the underside of leaves. The spots turn brown and later black. The centers of the spots can fall out leaving behind red edges around the holes. Infected leaves turn yellow and fall off. Powdery mildew is caused by a fungus that infects leaves with a powdery white growth. The severely infected leaves will become twisted or disproportional and curl upward. Tiny black dots form on the powder. The infection is spread through airborne spores.


Fungicide sprays can sometimes control disease.
Spray image by Dominator from Fotolia.com

Verticillum is difficult to control. Sometimes if caught early enough, a tree will recover from pruning the affected branches. If the tree is too infected, it must be removed. The fungus can survive several years in the soil so it is not recommended to plant a new tree in the same spot. Neither bacterial spot nor shot hole spot disease is easily controlled. It is recommended not to plant young trees near old ones. A fertilizer without excess nitrogen is recommended. Nitrogen can promote disease development. Powdery mildew can be controlled with the fungicide benomyl


About the Author


Sheri Engstrom has been writing for 15 years. She is currently a gardening writer for Demand Studios. Engstrom completed the master gardener program at the University of Minnesota Extension service. She is published in their book "The Best Plants for 30 Tough Sites." She is also the online education examiner Minneapolis for Examiner.com.