STEM AND BRANCH DISEASES

Ch14 10/5/99 2:19 PM Page 350
350 CHAPTER 14
Two other terms are used to describe decay: incipient and advanced decay.
In the early stages of decay, incipient decay stain typically develops, which usually
is brown or reddish-brown. In this case the wood is still firm to touch but the
fungus causing the decay is well established. As the decay progresses the wood
loses it structural integrity, is soft to touch, and can be easily penetrated with a
sharp tool or even a finger. This is advanced decay.
Important Decay Fungi
Table 14.3, on pages 352–353, shows some important Basidiomycete decay fungi,
common names, the type of decay they cause, and their hosts. There are so many
decay fungi that all of them cannot be listed or discussed here. Many butt rot fungi,
such as Heterobasidion annosum, Armillaria spp., Phellinus weirii, and Phaeolus
schweinitzii also cause root rots and they are discussed in detail in Chapter 12.
The fruiting bodies or conks of several common decay fungi, including Phellinus
pini, Ganoderma applanatum, Phellinus igniarius, and Laetiporus sulphureus are
shown in Figures 14.9 to 14.12, respectively. Excellent illustrations of the conks
of decay fungi are shown in Sinclair et al. (1987), Allen et al. (1996), and Hansen
and Lewis (1997).
Spread of Decay Fungi
The life cycle of a typical Basidiomycete decay fungus is shown in Figure 10.10.
Decay fungi produce either annual fruiting bodies or perennial conks. Most are
spread by airborne spores that enter through infection courts. A few produce
conidia. Spores usually enter through fire scars, wounds, branch stubs, cankers,
mistletoe infections, and galls. Wounds result from broken tops, treefall scars, bark
beetle attack (e.g., fir engravers), animal damage (caused by deer, elk, cattle, bears,
and porcupines), logging damage, pruning, and vandalism (carving and hatchet
marks). Once the spores have germinated and invaded wounds, the fungus spreads
vegetatively by mycelium. The spread usually is slow, less than 10 cm/year,
Figure 14.9
Fruiting body of Phellinus
pini.