Brown Fungus on the Trunk of a King Sago Palm

Phytophthora Fungi

• A King Sago palm suffering from either collar, foot, root, or crown rot is likely to display a brown fungus on the trunk of the tree. All four problems are caused by different species of Phytophthora fungi. These pathogens produce a stain or canker on infected trunks and a brown or gray discoloration underneath the bark of damaged areas. In addition, a brownish, black or red sap oozes from infected bark on the Sago palm.

Damage

• The disease stunts the growth of the sago palm and contributes to its decline with dieback of twigs and branches and the potential death of the entire specimen. The Phytophthora fungi can only exist when the soil surrounding the tree is exceptionally moist. The temperature of the environment also plays a significant role, with some species of Phytophthora demanding cool temperatures and others warm. The fungus generally lives in the soil for many years and enters the King Sago palm through the roots or crown.

Diagnosis

• A Phytophthora infection is confirmed by slicing away the bark around the stain or brown fungus. The area between the healthy white wood and the diseased, brownish-red wood will appear to be somewhat mushy and water-soaked, while an inspection of the roots infected by Phytophthora will show them to be firm but brittle. Roots that are simply being affected by too much water -- rather than a Phytophthora infection -- will be soft.

Management

• A brown fungus on the trunk of a King Sago palm is reason for extensive concern. Not only is it likely to prove fatal to the individual specimen, but the disease transfers easily to adjacent trees and plants. The best prevention is to ensure that the soil is well-irrigated and rarely overwatered. Mechanical devices like pruning shears and shovels must be sterilized to prevent spread of the disease. Application of fungicides also proves helpful in controlling the effects of root and crown rot.