Heterobasidion annosum

Appearance

The fruiting bodies of the fungi, which are also known as basidiocarps, are whitish around the margins, with button shaped pads, and dark brown on the upper surface. This fruiting body is created from mycelium, the mass that forms around the vegetative portion of the a tree body, i.e. that part of the tree with no differentiation like stem, leaves, or in this case roots. Basidiocarps are about 40 cm in diameter and 3.5 cm thick. The lower surface of the fruiting body is made of visible pores that are between 5 mm and 26 mm. Sexual spores are created from the basidiocarps, called basidiospores. Conidiospores occur in the asexual stage and are produced on conidiophores. Conidiospores and basidiospores are both produced by fungus, the latter being more important for infecting the conifers.

Behavior

In the summertime, basidiospores, the primary infective propagules, are released. These basidiospores are carried long distances by wind currents. They infect trees through damage such as freshly cut stumps. Once on the stump the fungus colonizes and moves into the root via mycelium. The ''Heterobasion annosum'' moves short distances from the roots of an infected stump through root grafts with other trees. It can also spread through insects that feed on roots.
Since this fungus can not move very far through soil, it relies on tree roots to help it infect neighbouring trees. In these roots, it can grow 0.1–2.0 m per year. This results in a spread of the fungus and disease gaps in the forest. These disease gaps are produced when the trees dies and falls, creating gaps in the forest canopy. These gaps affect the moisture and sunlight available, altering the habitats for plants and animals on the forest floor. ''Spiniger meineckellus'', the name for of the asexual stage of this fungus, is produced on stumps when the conditions are moist, and the conidiospores that are produced will be able to live in the soil for up to ten months. The role of conidiospores is unknown in the infection process and is not thought to be important.

Habitat

In the summertime, basidiospores, the primary infective propagules, are released. These basidiospores are carried long distances by wind currents. They infect trees through damage such as freshly cut stumps. Once on the stump the fungus colonizes and moves into the root via mycelium. The ''Heterobasion annosum'' moves short distances from the roots of an infected stump through root grafts with other trees. It can also spread through insects that feed on roots.
Since this fungus can not move very far through soil, it relies on tree roots to help it infect neighbouring trees. In these roots, it can grow 0.1–2.0 m per year. This results in a spread of the fungus and disease gaps in the forest. These disease gaps are produced when the trees dies and falls, creating gaps in the forest canopy. These gaps affect the moisture and sunlight available, altering the habitats for plants and animals on the forest floor. ''Spiniger meineckellus'', the name for of the asexual stage of this fungus, is produced on stumps when the conditions are moist, and the conidiospores that are produced will be able to live in the soil for up to ten months. The role of conidiospores is unknown in the infection process and is not thought to be important.