Agarwood, or gaharu, is the name of the blackened, fungal-infected heartwood of several species of Aquilaria trees in Southeast Asia. The resinous wood is an extremely valuble forest product used for incense and perfumes. Once an infected Aquilaria tree is located in the forest, the tree is felled and the heartwood chopped into small pieces (shown above). This material is then fermented in a solvent for several days and then distilled to extract the essential oil. The image below is from the agarwood plant in Pak Kading, the largest facility of its type in Laos.
The inability to tell whether an Aquilaria tree has been infected by the fungus or not has led collectors to fell any gaharu tree that they find, and wild populations of this species are, as a result, severely threatened by over-harvesting. The species is currently included in Appendix II of the CITES list. [NOTE: Most of the agarwood processed in Laos comes from inoculated material grown in plantations].