Report on Study of Diseased White pine in East Tennessee

Wien

1972

S. 195-206

4 Abb., 4 Tab., 8 Lit. Ang.

Unselbständiges Werk

200144516

In 1956, TVA started investigating a white pine disease first observed in east Tennessee in 1955. This study supplemented other investigations by the U.S. Forest Service and provided additional insights into the nature of the disease. It confirmed the conclusion that the causal agent is airborne and of abiotic origin, and that resistance of individual trees is genetically controlled. Although efforts were made to associate disease occurrence with industrial effluents, that atmospheric constituent causing the disease was not determined. Principal symptoms were premature shedding of older needles, stunted shoot growth, short needles, and discolored foliage. Needle tip dieback was frequently but not always present. Growth of diseased trees was poor; and there was some indication of a reduction in height growth of apparently healthy trees. Disease-susceptible white pine ramets deteriorated on plots in the affected area. They recovered when moved to remote locations. Conversely, disease- susceptible ramets on the remote plots remained healthy until moved to within the affected zone where they also began to fail. By 1965 approximately 10 percent of dominant and codoinant trees on the permanent study plots had died from the disease. Practically all of these had exhibited some abnormality in the beginning. Although trees continued to die, the total number of severely diseased and ded trees remained relatively constant after 1961. Timber mortality apparently has been restricted to white pine, which is a minor component of timber stands in the area, comprising less than 5 percent of the total merchantable volume.