Question: why are the leaves falling off my plum tree?
Answer: Improper watering practices – Watering properly is important to prevent leaf drop. ... A number of fungal diseases may also contribute to lost leaves on a plum tree, and these include: Armillaria root and crown rot, Phytophthora, and Verticillium wilt. Foliar diseases, such as plum leaf spot, may be the culprit too.