Effects of laminated root rot infection level and chemical fumigants on survival and growth of Douglas-fir near Apiary, Oregon

Laminated root rot caused by Coniferiporia weirii is a significant disease of western conifers; it is important to understand the effects of the disease on tree growth and survival and, for some management objectives, to develop treatments that will reduce those effects. This study was conducted in a 47-year-old Douglas-fir (Pseudotsuga menziesii) stand in northwest Oregon (near Apiary) between 1981 and 1991 (Harrington and Thies 2007). We evaluated the effects of root system infection on diameter and height growth, and also evaluated the effects of nine fumigation treatments on tree growth. Data include, but are not limited to, tree height, diameter at breast height, annual growths, vigor ratings and root disease infection rates.Coniferiporia weirii, the cause of laminated root rot, is a widespread root pathogen of conifer species throughout the northwestern United States and British Columbia, Canada. The fungus attacks live roots and can cause tree death either directly, by reducing the amount of functioning root system, or indirectly, by increasing tree susceptibility to windthrow. Previous management strategies to reduce the effects of laminated root rot focused on favoring tree species that are immune or resistant to the disease or reducing inoculum by stump removal. This study tested chemical injection as a possible alternative control method. The study also looked carefully at the effects of root infection levels (determined by root excavation and evaluation) and tree growth prior to excavation.Other aspects of this study are also described in Thies and Nelson (1996).