Pitch canker, a monocyclic disease caused by the fungus "Fusarium circinatum" (previously named "Fusarium moniliforme" var. "subglutinans"), was first described in 1946 by Hepting and Roth. When it was first described, disease levels were low until the 1970s, when a massive epidemic of pitch canker caused mass tree mortality in Florida slash pine. Some hypotheses suggest that the pathogen may have originated in Mexico and was then introduced in Florida and later transmitted to California on diseased seed. The pathogen has been reported in Mexico, however, high fungal diversity and low tree mortality from the disease suggests that this pathogen may have co-evolved in Mexico before being introduced to other parts of the world. Many reports describe the pathogen as endemic to Florida, likely because the disease was introduced a long time therefore the population has become more diverse. By 1974, over half of the slash pine population in Florida was infected with "Fusarium circinatum" disease. In areas where the pathogen is newly introduced, the fungal population is mostly clonal, because fewer mating types are present within the population, so sexual reproduction may be lower. Pitch canker infects nearly all pine species, including longleaf pine, shortleaf pine, and eastern white pine.