These are wood-decay diseases. They may get in through wounds in the lower part of the tree or penetrate roots directly. They involve the roots and in some cases the butt also. These fungi can travel from one tree to another using airborne spores and soilborne infested stumps and root systems. They can be separately called Armillaria, Annosum, Phytophthora, littleleaf, laminated root rots and others.
Recognition: Conifers with root rots generally die outward from a center point, from rotten snags to fresh dead to dying to sickly to healthy. This is called the "chronosequence of mortality". Insects, lightning and wind damage will not do this. Crown symptoms are stress crop of cones, limited growth causing a flattening of the crown and thin, yellowing foliage.
Prevention: There is no cure for most root and butt rots. When symptoms become visable much of the damage is already done and salvage or removal or the tree(s) is advised. Planting resistant trees, reducing tree densities by thinning and applying borax to stumps can help. Only thin between May and August when infection risk is minimal.
Control: Inoculum reduction is about all you can do for most root disease. It is expensive and only done in high value areas. That means various treatments that may involve stump removal or fumigation. Stumping is limited by terrain for equipment. Fumigation is more experimental.
