Decay of heartwood is very common especially with older trees. With this type of decay there are two types of general rots.
White rots cause affected wood to become pale, soft and punky.
Brown rots cause affected wood to become dark, firm and chunky. Hollow trees may result of successive wood rots over several years. The sporocarps or fruiting bodies of the fungi that cause these rots usually are shelf fungi or mushrooms. If is very difficult to determine the identity of a fungus causing a wood rot unless a sporocarp is present. Wood rots do not reduce the vigor of the tree, but do reduce the strength of the wood.