Fig. 19.1. Witches' brooms on the killed overstory ponderosa pine once provided abundant inoculum of dwarf mistletoe seed for infection of the understory, thus assuring the continued presence of the pathogen on this site (Photo: T.C. Harrington)
Fig. 19.2. A lodgepole pine stand heavily infested with dwarf mistletoe has abundant fuelwood, and a subsequent fire would tend to favor pine regeneration. But if fire is suppressed, the more shade tolerant and dwarf mistletoe resistant spruce in the understory will eventually replace the pine (Photo: T.C. Harrington).
Fig. 19.3. Armillaria ostoyae clones may expand through root-to-root spread for centuries, causing circular infection centers of conifer mortality. The clone at the bottom of the hillside in the lower left of the picture is nearly 8 hectares in area. (Photo: R. Williams).
Fig. 19.4. Rings of mortality of overstory mountain hemlock in the Cascade Mountains of Oregon (USA ) are caused by individual clones of the root rot pathogen Phellinus weirii. The more root disease resistant lodgepole pine regenerates (foreground) in the wake of the mortality (Photo: T.C. Harrington).
Fig. 19.5. Blister rust has all but eliminated western white pine from this stand in Idaho (USA), leaving the root disease prone Douglas-fir and grand fir. Cones of a surviving white pine in the center have been bagged for controlled pollination (Photo: T.C. Harrington).
Fig. 19.6. Pictch canker has proven to be a serious introduced disease on radiata pine in California. A stem canker on a radiata pine on the Monterey Peninsula shows extensive pitching (Photo: R. A. Blanchette).
Fig. 19.6. Pine shoot blight caused by Sphaeropsis sapinea can result in tip dieback and mortality of exotic pines planted outside of the native range of pines, such as the Iowa State University campus (Photo: T. C. Harrington).
Fig. 19.7. Brown spot needle blight has caused extensive damage to pines planted as exotics and has been a management problem for longleaf pine in the southeastern USA (Photo: T. C. Harrington).
Fig. 19.8. Extensive mortality in Japan has been attributed to the introduced pine wood nematode. The mortality here is on Shikoku Island (Photo: T. C. Harrington).
