Formation of agarwood

here are fifteen species in of the Aquilaria genus and eight are known to produce agarwood.^[5] In theory agarwood can be produced from all members; however, until recently it was primarily produced from A. malaccensis. A. agallocha and A. secundariaare synonyms for A. malaccensis.^[1] A. crassna and A. sinensis are the other two members of the genus that are usually harvested.

Formation of agarwood occurs in the trunk and roots of trees that have been infected by a parasitc ascomycetous mould,Phaeoacremonium parasitica^[6], a dematiaceous (dark-walled) fungus. As a response, the tree produces a resin high in volatile organic compounds that aids in suppressing or retarding the fungal growth. While the unaffected wood of the tree is relatively light in colour, the resin dramatically increases the mass and density of the affected wood, changing its colour from a pale beige to dark brown or black. In natural forest only about 7% of the trees are infected by the fungus. A common method in artificial forestry is toinoculate all the trees with the fungus.

High quality resin comes from a tree's natural immune response to a fungal attack. It is commonly known as agarwood #1 (first quality). An inferior resin is created using forced methods where aquilaria trees are deliberately wounded, leaving them more susceptible to a fungal attack. This is commonly called agarwood #2.