Treesearch

Associations between root diseases and bark beetles (Scolytidae) constitute some of the most serious pest complexes affecting forests in North America and elsewhere. The interactive functioning of these pests derives from the following relationships: 1) root diseases predispose trees to bark beetle infestation by lowering resistance, and perhaps increasing attractiveness, of trees to the attacking beetles; 2) bark beetles may be vectors of root disease fungi or may create infection courts for them.

Annosus root disease (ARD), is the major root disease of pines in the southeastern United States where severely affected trees exhibit growth loss. Assessing the potential damage of ARD is essential for making effective disease control and management decisions. A soil hazard rating system developed to identify potential for tree mortality is described. The Annosus Sampling Procedure accurately estimates the severity of ARD within a stand. The GY-ANNOSUS computer program estimates growth loss caused by ARD. ARD management strategies are discussed.

An evaluation of basal area increment was made in 1988 of six pine plantations located across the southeastern United States. These plantations had been thinned in 1969-1970 and stumps treated with borax to measure long-term efficacy of annosus root rot control. In the present study, no long-term growth effects were identified. There were neither negative growth effects of residual infection in surviving trees nor were there positive growth effects in trees which were released as a result of tree mortality. These results suggest that effects of inoculation and control treatments may have...

In 1979, an equation was developed to estimate the percentage of current and future timber volume loss due to stem decay caused by Heterobasidion annosum and other fungi in advance regeneration stands of grand and white fir in eastern Oregon and Washington. Methods for using and testing the equation are presented. Extensive testing in 1988 showed the equation to be valid for estimating volumes of timber loss due to stem decay in grand fir stands in northern Idaho, in white fir stands in southern Oregon and northern California, in red fir stands in northern California, and in western...

True fir stands in California (3.5 million acres) were surveyed during 1979-1980 to estimate the prevalence of infection by Heterobasidion annosum, and to determine stand and tree characteristics associated with the occurrence of annosus root disease. Approximately 4 percent (1.46 billion board-feet) of the live true firs were estimated to be infected by H. annosum; dead firs associated with the fungus were estimated to be 25 percent (68 million board-feet) of the total dead firs during a 1.5-year period. Annosusroot disease was estimated to infest 18 percent of the surveyed area (632,000...

Approximately 12.5 percent of California commercial forest land is infested with Heterobasidion annosum, resulting in annual losses of approximately 111 million board feet. The east side of the Sierra Nevada/Cascade Crest in northeastern California is most severely affected, with about 20percent of the land out of production because of annosus root disease. In Yosemite Valley, 158 annosus root disease centers were identified. These centers are enlarging at an average rate of 0.67 m/yr. The most important impact of annosus root disease in recreation areas appears to be hazard and the loss...

An argument is advanced to suggest that infection and damage caused in coniferous forests by Heterobasidion annosum are markedly less severe, and survival of the fungus less common, under cool, wet conditions than in other climates. This premise is supported by the author's incisive insights, experience in southeastern Alaska, and data from this area and from other sources. In general, frequent rains reduce the population of airborne spores and wash many of them from stump surfaces. Cool temperatures reduce evaporation of water which helps to maintain a high moisture content in stumps that...

Heterobasidion annosum infects western hemlock (Tsuga heterophylla) and causes a root and butt-rot disease. A disease survey was initiated in thinned Southwestern Washington hemlock stands to determine current disease incidence caused by H. annosum.

Annosus root disease affects three tree species groups in the Pacific Northwest-the hemlocks, the pines, and the true firs. The disease causes significant decay and stem breakage in old growth western hemlock stands but little damage in young managed stands. Losses in ponderosa pine are minor over most of the region but can be substantial in selectively harvested stands on dry plant association types in southeastern Oregon. Annosus root disease is very damaging in white and grand fir stands east of the Cascades. The disease may limit management of these species in stands that have experienc...

Stumps of Douglas-fir, western hemlock, Sitka spruce, and amabilis fir were sampled in precommercially thinned stands to determine the percentage of stump surface area colonized by Heterobasidion annosum. There were significant differences among species in the percentage of stumps colonized. Seasonal patterns were evident for each species; however, differences were not significant. Both the percent incidence of infection and the percentage of surface area colonized increased with increasing stump diameter. The results indicate that stump treatment to prevent infection is not necessary for...