I was wondering if you might be able to tell me what is going on with my plum tree and how I might be able to help it. From the attached pictures it seem 1/2 of it might be dying.
While it is very difficult to diagnose the problem from your photograph, the following are among the conditions that may be affecting your plum tree:
- Verticillium wilt, a fungal disease, caused by the fungi in soil which affects many plants including plums. Infection causes leaves to yellow and drop, often with a wilted appearance. The disease begins at the roots of the tree, progressing upward, and individual branches’ dieback may also occur. It is usually manifests in early summer as a progressive loss of leaves from infected limbs, starting at the base of each branch. The leaves may die and stay on the branches, or they may become yellow and dull in appearance before dropping prematurely. An entire tree may show these symptoms, or infection may be confined to one side, or even one branch, of the tree. The most significant diagnostic symptom of verticillium wilt is found when branches or twigs are cut open as wood affected by the disease will show in the cross section as a series of light to dark brown, irregularly shaped spots. Unfortunately, there is no cure and verticillium wilt is generally treated by removing the affected plant or tree at ground level. As the fungus persists in the soil, future plantings should be of plants/shrubs/trees resistant to the disease.
- Fusarium wilt, another fungal disease, which also causes leaves to yellow and stems to drop. Leaves typically drop early. Sometimes the symptoms are most noticible on one side of the plan. Again there is no treatment and the affected plants should be removed. The fusarium fungi can also survive in soil for a few year so only resistant plants should be planted as replacements.
- Bacterial leaf spot where spots or patches develop on the leaves, the leaves are killed and may drop. It can be treated by removing the affected leaves, including cleaning away the leaves in fall.
- Shot hole disease, caused by fungi or bacteria. With this disease discoloured spots, typically brown, develop on the foliage. Dead tissue in the foliage falls away leaving holes. As this condition affects plants which are lacking vigor it can be treated by trying to improve the over-all health of the plant by improving general growing conditions, i.e. making sure it is watered particularly in hot weather, feeding with a high nitrogen fertilizer in the spring and mulching annual with well-rotted manure or compost.
- An aphid infestation can also cause leaf drop. This can be treated by a spray of water to displace aphids and application of dormant oil in early spring.
As you can there there are different possible causes; some treatable, some not. Correct diagnosis would require an examination. I suggest that you contact a certified arborist, who will be able to diagnose what ails your tree and inform you about possible remedies. Here is a link which could assist you in finding an arborist: