The fungus Phellinus badius forms large quantities of the toxic organohalogen drosophilin A methyl ether (DAME), using chlorine ions from the heartwood of the mesquite tree. DAME occurs as clusters of glassy crystals up to 1 millimeter (.039 inches) long within decayed wood and is also found in high concentrations in the fungal fruiting bodies. It is insoluble in water and can persist in decayed wood or soil for many years, even upon exposure to weathering. Ground fires can volatilize DAME, which can subsequently condense on the cooler parts of the smoldering logs. It was the overpowering smell of DAME in a smoldering mesquite forest after the Pickett fire east of Phoenix, Ariz., that led to the discovery of these crystals. The amount of DAME released to the atmosphere through biomass burning is unknown, but could be significant. There is a large market for charcoal made from mesquite, much of which is produced in Mexico from large, mature trees that are often subject to decay. Charcoal production could be a significant source of atmospheric release of this compound. DAME production is not limited to P. badius but has been associated with other wood decay fungi, suggesting a substantial natural reservoir of this compound with probable environmental significance. Global climate change, with hotter and drier weather in western North America, could extend the range of mesquite and exacerbate this problem.