Scientists now believe that the Salem witch hunts of 1692 may have initially been caused by an infestation of a microbiological poison: The fungus Claviceps purpurea, commonly known as rye smut that produces the poison ergot. When ingested, this poison produces symptoms similar to those exhibited by the girls who accused others of being witches in Salem. Historians and biologists have reviewed environmental conditions in New England from 1690 to 1692 and have found that conditions were perfect for an occurrence of rye smut overgrowth, as the weather was particularly wet and cool. In addition, rye grass had replaced wheat as the principal grain because wheat had become seriously infected with wheat rust during the cold and damp weather. The symptoms of ergot poisoning include convulsions, pinching or biting sensations, and stomach ailments, as well as temporary blindness, deafness, and muteness.