Fruit bodies of Ganoderma spp. frequently causing decay, together with important morphological features as seen in pure culture. A-B) Ganoderma lipsiense: Perennial fruit body and mycelium without strands (arrow); diameter of peripheral hyphae: 3.5 µm. C-D) Ganoderma adspersum: Perennial fruiting body and mycelium with strands (arrow); diameter of peripheral hyphae: 2.1 µm. [Photo credit: Francis W.M.R. Schwarze]

Bracket fungi of the genus Ganoderma are known by mycologists for the crust-like upper surfaces of their fruit bodies, which in some species, such as G. pfeifferi and G. resinaceum, have a varnished appearance. Arborists and managers of plantation crops know them collectively as a cause of decay in a very wide range of tree species and palms all over the world (Phillipi 1893). Among amenity and roadside trees, their presence is often taken to indicate that a hazard assessment may be necessary.

Ganoderma spp. are known to produce pharmacologically active compounds and enzymes used in bioremediation and bioenergy production (Kües et al. 2015). The genus Ganoderma belongs to the family of the Ganodermataceae within the Basidiomycetes ('higher fungi'). Its members possess a trimitic hyphal system, which consists of binding, skeletal and generative hyphae. All Ganoderma spp. cause a white-rot, but they can degrade the woody cell walls in a number of ways, including selective delignification and simultaneous rot (Schwarze & Baum 2000). Ganoderma lipsiense (Batsch) G.F. Atk. Ganoderma lipsiense is widespread in the northern hemisphere. It has a broad host spectrum, mainly consisting of deciduous genera, e.g. Acer, Fagus, Tilia, Populus, Platanus, Quercus, Aesculus, Betula, Alnus, Fraxinus, and Salix, but also occasionally including conifers such as Abies and Picea. It commonly causes a root and butt-rot but, being confined mainly to trees with dysfunctional xylem associated with large wounds on the roots, it is regarded as predominantly saprotrophic.

The perennial fruit bodies of G. lipsiense are often confused with those of G. adspersum, but the following characteristics can help to differentiate these species: If the lower surface of the fruit body bears the galls of the larvae of the mushroom fly Agathomyia wankowici, the fungus can be identified as G. lipsiense, as it is the only European species of Ganoderma affected (Breitenbach & Kränzlin, 1986). However, the absence of these galls does not prove the converse, especially in regions where the fly does not occur. Another feature of the fruit bodies of G. lipsiense is that they are usually thinner than those of G. adspersum (20 - 60 mm, compared with 40 - 100 mm) at the base. In addition, their undersides tend to emerge sharply at right angles from the host stem, whereas those of G. adspersum usually have a decurrent attachment. Moreover, G. lipsiense has a thinner crust, which can be indented with a fingernail. With a hand lens, a difference in the pore structure can be seen in a radial section; in the older parts of the fruit body, the pores of G. lipsiense, become filled with a white mycelium, whereas those of G. adspersum remain empty (Breitenbach & Kränzlin, 1986).

Microscopic features are also useful in distinguishing G. lipsiense from G. adspersum. The basidiospores of G. lipsiense are, on average, smaller (7 - 9 x 4.5 - 6.0 µm, compared with 8.5 - 12.0 x 6.5 - 8.0 µm) (Breitenbach & Kränzlin, 1986). Also, it has been reported by Schwarze & Ferner (2003) to produce broader hyphae at the growing margins of pure cultures on agar, having an average diameter of 3.50 µm, compared with 2.10 µm in G. adspersum.