Juniper Pocket Rot
The fungus is a white heart rot that decays the non-living core of the tree and spreads primarily by spore dispersal. Generally heart rot fungi do not penetrate sound trees but require an opening into the heartwood to invade through. Any opening into the heartwood or exposed dead sapwood adjacent to heartwood is a potential site for fungi to become established. The most important wounds that generally spread heart rots are mostly caused by fire and human activity. Pruning appears to be one of the primary sources of entry of this disease into Utah junipers seen in Eastern Nevada. See figure 1 below showing a conk fruiting body right below the old pruning wound that infected this tree. This is especially common in campground trees.
Signs and Symptoms of Infection
The early symptoms of this disease are subtle. Often the tree when pruned shows a dark to light pink to red ring in the heartwood rather than the normal light colored heartwood. With more advanced decay, those same pruning wounds would reveal a number of small pockets filled with white to yellowish cottony fibers of decay and the tree’s foliage declines, thins out and only small tufts are seen near the end of the branches (see photo below). Conks (fruiting bodies from which fungal spores are disseminated) like the one below the pruning wound in the photo (above) indicate that decay is probably extensive throughout the stem The conk has an upper surface of the woody hoof-shaped fruiting body that is dark brown to nearly black in color. The lower surface is light brown, yellow to dull whitish with the center of conk being a deep reddish brown as seen in the picture above.
This heart rot at its advance stage can cause high mortality in various stands across the state and into western Utah. It causes center rot of the main trunks and branches which affects the structural soundness of the wood. This may make the tree unusable for fence posts or other post products.
Control & Prevention
Fungal diseases are difficult to control. The best way to prevent juniper from getting this disease is to prevent wounding on junipers.
Remove infected trees, avoiding any juniper wounding by removing whole trees when doing fuel reduction work. Emphasize the need to campground visitors the importance of not injuring the junipers in the area.