Ganoderma Butt Rot, Ganoderma lucidum (Curtis:Fr.) P. Karst.

Leininger, T.D; Solomon, J.D.; Wilson, A. Dan; Schiff, N.M. 1999. A Guide to Major Insects, Diseases, Air Pollution Injury, and Chemical Injury of Sycamore. Gen. Tech. Rep. SRS-28. Asheville, NC: USDA Forest Service, Southern Research Station. 44 p.

Importance.-This fungus is one of the most commonly observed causes of butt rot in southern hardwoods. A true pathogen, it is often responsible for premature death of residential and landscape trees. It can kill large trees and frequently causes decay in declining trees.

Identifying the Disease.Ganoderma lucidum causes a white, spongy soft rot of sapwood and heartwood in the roots and lower bole. Diseased trees eventually lose vigor, bear undersized leaves and dead branches, and sometimes have wilted or yellow leaves. However, fruiting bodies may form at or near the ground on apparently healthy trees.

Figure 36a. - Note the glossy, red-brown top and stalk of the G. lucidum fruiting body. Photo by Theodor D. Leininger, USDA Forest Service

Identifying the Fungus.-The upper surface of G. lucidurn’s large, reddish-brown fruiting bodies usually has a shiny, varnished look and a leathery texture (fig. 36a). The fruiting bodies may form singly or in overlapping clusters at ground level or on the lower bole of sycamores. The margins are white, becoming a tawny yellow with age. The lower surface of a fruiting body has pores. Brown spores released from fruiting bodies often form a dustlike coating on grass, bark, or the fruiting bodies themselves.

Biology.-Ganoderma lucidum infects trees through wounds on roots or the lower bole caused by tools, lawn mowers, and falling trees or limbs. The decay’s lethal effects occur when living cells in the sapwood are killed. A decay column may form for many years before sufficient damage causes visible symptoms in the crown. Fruiting bodies eventually form and may occur repeatedly during the summer months. Living trees with decay in the roots or lower bole are subject to windthrow (fig. 36b).

Figure 36b. - Advanced decay in this canker, along with insect and bird damage, poses a hazard. Photo by

Control.-This disease is best controlled by preventing mechanical wounds to the lower bole and roots. Care should be taken not to injure landscape trees, especially when using heavy equipment to clear land when preparing sites for home building.