Fungal & Decay on Trees	-- Signs of Decay --
Ganoderma applanatum -- Fungus invades tree through wounds, several fungal diseases, sometimes called heart or sap rots, cause the wood in the center of trunks and limbs to decay. Under conditions favoring growth of certain rot fungi, extensive portions of the wood of living trees can decay in a relatively short time (months to years). This significantly reduces wood strength and kills sapwood storage and conductive tissues. Almost all species of woody plants are subject to trunk and limb decay.
	Fruiting bodies (conks) of the wood-decaying fungus Ganoderma applanatum. Photo by Jack Kelly Clark.

Upper surface of conk is brown and the lower surface is white, but turns dark when scratched, hence the name artist’s conk. Stalks are absent. Fungus can spread through natural root grafting. Conks are usually found near ground level, but columns of decaying wood can extend as far as 15 feet above and below the conk.

Known as --   "The Artist's Conk"

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Identifying the Fungus.  --  This fungus is distributed widely on oak, elm, and other Texas species. It is common on older, living oaks in yards, parks, and along streets. While its ability to kill trees is questionable, it will decrease tree health over time.  Hoof-shaped conks (fruit bodies), the most reliable sign of diseased trees. Conks are dark brown to black on the upper surface with many small cracks, and light brown on the lower, pore surface. The interior of conks is dark brown with numerous white flecks. Conks are perennial: new layers of pores form on the lower surface each year; thus the interior of old conks appears layered. Although the absence of conks does not necessarily mean the absence of decay, several small conks or a few large conks usually indicate advanced decay. Young conks may grow around green leaves or show leaf imprints on top from where leaves lay on the growing conks. A yellowish liquid may exude from young conks, and old conks look like burned wood on top.

Identifying the Injury. -- Thinning crowns may result from long-term infections that degrade root systems. The slow crown deterioration weakens the tree and may lead to a more serious butt rot. This can lead to complete tree failure.
 

Biology. --   Following tree wounding, bacteria and non-decay fungi flourish on the exposed woody tissues, creating conditions for establishment of decay fungi. Windborne microscopic spores released for a few days to several weeks from conks on infected trees germinate on wounds through dead or scarred roots or through fire or home construction scars at tree bases and penetrate the tree and conks are produced.. The decaying stage of the rot fungi follows and conks will be produced. The rate of decay varies with the tree species, fungus, and wound size. Decay is most extensive when wounds are large.

Control. -- Because all infections occur through bark wounds, injury prevention is the primary approach to control. Severely decayed trees should be deadened. Consider early salvage for infected trees that have value because the lower, most valuable portion of the log is being decayed, with an increased susceptibility to insect attack, windthrow and degrade from stain. As with all root and butt rotters, bole and crown conditions should be monitored regularly for signs of weakening and possible breakage.  By the time conks appear, the fungus has been decomposing the wood for years. Breaking off the conk or removing the mushrooms does nothing to stop or delay the fungus or rate of decay. The majority of the fungus, the mycelium, is in the wood or cambium. Repair valuable urban trees by removing the decay, treating the cavity with a fungicide and filling it with a suitable material.
 

Yellowish-white wood surrounded by a zone discolored wood. This is characteristic of the early stage of decay.

Spongy wood, yellowish in color, surrounded by irregular black zones of discolored wood. This indicates advanced decay.