Why Does a Mulberry Tree's Leaves Turn Yellow & Drop?

Mulberry is a genus of flowering, temperate climate ornamental trees and shrubs valued for fast growth. Mulberry leaf yellowing and drop is a symptom of disease and nematode infestation. Identifying the cause of the problem and then taking steps for early control and, ultimately, prevention are vital to reducing the severity of these mulberry disorders.

Leaf scorch is a serious bacterial disease of mulberry that affects foliage and vigor of the plant. Leaf scorch, caused by the bacterium Xyllela fastidiosa, affects a variety of ornamental trees in landscape settings. Symptoms of the disease include brown scorched leaves, yellow leaf margins, leaf drop and branch dieback. The disease infects mulberry through insects that carry the disease from infected trees. Symptoms appear during middle to late summer. Increase plant vigor with regular watering and fertilization to prevent the disease. However, there are no chemical treatments for infected plants.

Root knot nematodes are microscopic roundworms that infect the roots of mulberry, causing extensive damage. While the infestation occurs below the soil surface, above ground symptoms indicate infection. Symptoms of infection include galls on roots, reduced vigor, leaf yellowing, leaf drop and plant death. Warm temperatures, irrigation and sandy soil favor severe nematode infestations. University-based and private labs can test for nematodes in soil samples before planting mulberry to prevent infestation. Clean your gardening equipment and use resistant varieties of mulberry to prevent and slow infection rates. However, no pesticides are available for root knot nematode control.

Sooty canker is a serious disease of mulberry branches and foliage, caused by the fungus Hendersonula toruloides. The fungus favors sunburn, pruning wounds, cracks in bark for infection, high temperatures between 85 to 105 F and weak trees for infection. Symptoms of infection include leaf wilt, leaf yellowing, cankers on limbs, branch dieback, leaf browning, leaf drop and tree death. Prune infected limbs to reduce the severity of the disease and maintain tree vigor to prevent infection. Copper-based fungicides applied on tree wounds are an effective method for sooty canker control.

Ganoderma root rot is a fungal disease caused by Ganoderma lucidum, whicht affects the vigor of weak mulberry trees. The fungus infects mulberry roots and open wounds, causing leaf wilt, leaf yellowing, leaf drop, visible fungal growth at the base of the tree and tree death. Avoid wounds and increase tree vigor with regular fertilization and watering to prevent infection. However, there are no chemical controls available after infection occurs. The fungus can survive in dead trees and soil; therefore, avoid planting mulberry trees in the same location as previous infections.