The typical signs of BRR disease are a) fruiting bodies of Phellinus noxius, b) mycelial encrustation, c) soil aggregates and d) mycelial nets. (a) The appearance, on lower trunk or roots, of brownish-black/dark greyish-brown colored imbricate or resupinate fruiting bodies of Phellinus noxius with their characteristic porous hymenium surface up-facing is an obvious sign of BRR infection. The sizes of fruiting bodies vary greatly ranging from 3-10 cm in length to 8-20 cm in width. The fruiting bodies of Phellinus noxius are the sexual stage of the fungal lifecycle and their development, under the right conditions, begin with the formation of the primordial stage. The developing fruiting bodies would continue to grow in size, reach a stage of maturity in bracket and/or resupinate forms from which basidospores are formed for dissemination, and end at senescence. There are occasions where the developing fruiting bodies become abortive and reach premature senescence without forming basidopsores.
If the mycelia of Phellinus noxius are spreading under the bark, or under the outer layer of roots, these parts can peel off easily. The diseased parts look rough with flaky appearance on their surfaces covered by a brownish-black mycelial encrustation. Normally, the mycelial encrustation can extend from the root collar to 1 m high on the tree trunk. There are also reported cases from the literature that mycelial encrustation can reach 2-3 m in height.
If fruiting bodies of Phellinus noxius and mycelial encrustation cannot be found, the bark of the entire lower trunk/root collar and the outer layer of all the roots of the suspected diseased tree should be examined. If necessary, cut open with appropriate tools (e.g. handheld adze, knife, etc.) upon soil excavation to check for soil aggregates and yellow, dark brown or brownish-black mycelial netting on the inner surface between the bark and the wood tissues