Forest Health > Insects and Diseases publication
Diseases of... Hardwood Stem
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HISPIDUS CANKER
Typical sporophores (conks) of Inonotus hispidus and callus folds or ridges of hispidus canker on the stem of an oak. (Old sporophore appears as dark brown mass at top of canker.)
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| Pathogens: |
Fungus Inonotus hispidus (formerly Polyporus hispidus) |
| Common Host: |
Oaks Quercus spp.,
Other Hardwoods |
Significance: |
Hispidus cankers are a noteworthy example of a group of tree diseases referred to as canker rots. These diseases are so named because they result in both internal stem decay (heart rot) and external cankers (flattened or depressed areas in the bark resulting from death of the cambium). Hispidus cankers are common in Florida, especially on laurel, southern red, and turkey oaks. Generally, hispidus cankers are not a significant forestry problem, but they often cause substantial damage to individual trees. The heart rot associated with hispidus cankers frequently renders infected trees vulnerable to stem breakage. Severely infected shade trees are often safety hazards. |
Recognition: |
Hispidus cankers generally appear as vertically elongate, flat or sunken areas (cankers) on the trunks of infected trees. The bark of these cankers faces usually remains firmly attached and conspicuous callus folds typically develop around the canker margin, giving infected stems an overall swollen appearance. Branch stubs or scars are common, although not necessarily detectable at or near the center of canker faces. During the late summer, fall, and early winter the pathogen produces large, spongy, bracket-shaped conks (sporophores) on the canker faces. Conks are yellowish-brown to rusty red or brown and somewhat watery when fresh. Dense, somewhat stiff, tufted, or matted hairs cover the upper surface of the conks. The lower, spore-bearing surface is porous. As the conks age they shrink, darken to nearly black, harden, and often fall from the tree. Remnants of old conks are often detectable months later, either still attached to canker faces or lying on the ground at the bases of infected trees.
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Infection Biology: |
Hispidus infections occur primarily through dead branch stubs on the stems of susceptible hosts by means of aerially disseminated spores. Presumably, some infections occur through trunk and branch wounds as well. The fungus develops first in the heartwood of its hosts and later grows outward into the cambium, killing it and causing the readily visible, characteristic cankers. Spores for the initiation of new infections are produced in the pores on the undersurfaces of the typical conks produced later on the canker faces. |
Control: |
No effective therapeutic treatment is known for trees infected with Inonotus hispidus. Control strategies in both forest and urban settings must be based on the concepts of prevention, sanitation, and salvage. In forestry operations, harvest and salvage infected stems where practicable. In timber stand improvement operations, fell infected trees to minimize sporophore production and spore dispersal. Removal or felling of infected trees provides the additional benefits of reducing competition for the more desirable, disease-free trees and reducing the risk of injury to healthy trees through stem breakage and falling of cankered trees. Avoid unnecessary logging or other injury to stems of susceptible host species
In urban or landscape situations, identify and remove trees with hispidus cankers as hazard trees with respect to stem breakage and inoculum reservoirs (i.e., sources of infectious spores).
Time pruning of host tree species so as to minimize exposure of susceptible tissues:
(a) prune stem branches when sufficiently small to facilitate the healing process of callus formation;
(b) perform such pruning in late winter or spring when spores of the pathogen are not being disseminated. Avoid unnecessary injuries to stems of susceptible trees. |
Bulletin No. 196-A | Printed October, 1983 | Contact the Forest Health Section |
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