Fruiting body of brown cubical root and butt rot of pine.
The fungus enters living hosts through damaged roots, fire scars, and other wounds near the tree base. The initial stage of decay appears as a light yellow stain. In the advanced stage, the heartwood becomes brittle and breaks into large yellow-brown to reddish-brown cubes. The fungus develops primarily in the roots and butt and seldom extends more than 15 or 20 feet up into the stem. Diseased trees are subject to wind-throw and wind breakage. Although the volume of wood destroyed by the rot is small, the total volume lost through wind-throw is quite large. Mature, suppressed, and weakened off-site trees are commonly attacked by the fungus. It is assumed that the fungus may also spread from infected to healthy trees through root contacts and grafts. The only outward signs of decay are the annual sporophores, which develop in late summer and fall during moist weather. Conks formed at the base of infected trees are bracket shaped, while those arising from decayed roots appear circular, sunken in the center, and supported by a short stalk. When fresh, the upper surface is velvety, concentrically zoned, and reddish-brown in color with a light yellow margin. The underside is dark olive or green with large irregular pores.
In forest stands, no method of controlling the disease is known. Losses may be prevented to some extent by reducing the amount of root damage and wounding from heavy logging equipment. The prevention of basal fire scars in conifer stands will also reduce the incidence of this disease. Trees which show signs of advanced root and butt rot should be removed from around recreation areas, parking lots, power lines, and buildings to avoid damage from wind-throw and wind breakage.
RED ROOT AND BUTT ROT
Fruiting body of red root and butt rot of pine.
Polyporus tomentosus causes red root and butt rot of living conifers throughout North America. Common hosts of the fungus are: spruce, larch, pine, fir, Douglas fir, hemlock, and cedar. Throughout the southern United States, P. tomentosus has been reported in two general areas; causing extensive degrade of mature shortleaf pine in northern Arkansas and root and butt rot of slash pine in South Carolina, Georgia, and Florida.
The fungus is believed to enter living hosts through basal wounds and damaged roots. Under ideal conditions, the fungus may spread from infected to healthy trees by way of root contacts or grafts. Growth of the fungus is very slow, often causing host mortality 20 to 30 years after initial infection. Wood decayed initially appears firm, but dark reddish-brown in color. In advanced stages, the wood is flecked with elliptical white pockets separated by brown-colored wood. Infected conifers generally express typical root rot symptoms. Trees show evidence of reduced radial and internodal growth, accompanied by death of the crown from the base upward. The foliage appears off-color and reduced in length. Under moist conditions, sporophores are produced either at the base of infected trees or on the forest floor. Bracket-shaped sporophores are produced at the base of infected trees while stipitate conks are produced on the ground directly over infected or dead roots. Fresh sporophores appear yellow-brown in color from above with a lighter colored pore surface below.
No effective method of controlling the disease in forest stands is presently known. However, damage and losses may be reduced by management practices which reduce or eliminate the chance introduction of the disease into healthy stands. In areas where red root and butt rot is common, attempts should be made to conduct logging and thinning operations during the dry season to avoid mechanical damage to the root systems of the residual trees.