Unlike other similar fungi, there are no rhizomorphs. They are formed above ground on the encrustation on the trunk. Sporophores are very rare, large, hard purplish-brown bracts with yellowish-white growing margins and concentric blackish zones towards the edges. It is one of several fungi associated with heart or butt rots of forest and timber trees ( Ivory, 1996). In advanced stages of decay, the wood becomes light, dry and friable and honeycombed. In the diseased wood, dark lines are visible due to the presence of the fungal hyphae. The fungus moves towards the collar of the tree and occasionally the encrustation may be visible above ground level. This consists of brown mycelium in which soil and small stones are firmly embedded.
The most characteristic symptom of this disease is the brown encrustation covering the surface of the diseased roots. Symptoms may develop slowly or the tree may wilt and become defoliated in only a few days. The leaves of an infected tree yellow and wilt and typical dieback symptoms result. noxius attacks a wide range of tropical plants, although mostly trees. Skeletal hyphae 5-9 µm diameter, unbranched, of unlimited growth, with a thick reddish-brown wall (up to 2.5 µm thick) and continuous lumen, non-septate. Generative hyphae 1-6.5 µm diameter, hyaline or brownish, wall thin to somewhat thickening, freely branching, simple septate. Hyphal system dimitic with generative and skeletal hyphae, non-agglutinated in the context, but strongly agglutinated in the dissepiments. Tramal setal hyphae diverging to project into the tube cavity, 55-100 x 9-18 µm, with a thick dark chestnut-brown wall (2.5-7.5 µm thick) and a broad obtuse apex. Context setal hyphae radially arranged, up to 600 x 4-13 µm, unbranched or rarely branching, with a thick dark chestnut brown wall and capillary lumen apex acute to obtuse, occasionally nodulose. Setal hyphae present both in the context and the dissepiment trama. Basidia 12-16 x 4-5 µm, short clavate, 4-spored. 4 x 3 µm, ovoid to broadly ellipsoid, hyaline, with a smooth, slightly thickened wall, and irrgular guttulate contents. Pore surface greyish-brown to umbrinous pores irregular, polygonal, 6-8/mm, 75-175 µm diameter, dissepiments 25-100 µm thick, brittle and lacerate tubes stratified, developing 2-5 layers, 1-4 mm to each layer, darker than context, carbonaceous. Context up to 1 cm thick, golden brown, blackening with KOH, silky-zonate fibrous, woody. Pileus 5-13 x 6-25 x 2-4 cm, applanate, dimidiate or appressed-reflexed upper surface deep reddish-brown to umbrinous, soon blackening, at first tomentose, glabrescent, sometimes with narrow concentric zonation, developing a thick crust margin white then concolorous, obtuse. Basidioma perennial, solitary or imbricate, sessile with a broad basal attachment, commonly resupinate.