The Incidence of the Genus Myrothecium in New Zealand Pastures and Its Relation to Animal Disease

Summary: Four species of Myrothecium, in descending order of frequency Myrothecium leucotrichum, M. verrucaria, M. cinctum and M. roridum, occurred on leaves of perennial ryegrass, white clover, kikuyu grass and mixed pasture in the North Island of New Zealand. Myrothecium cinctum was particularly common on kikuyu grass, but otherwise plant species did not appear to affect their distribution. Numbers were greatest under warm conditions, in summer and autumn. No isolates were recovered from samples from the South Island. Cultures of most isolates of M. verrucaria, of some of M. roridum, of a few of M. leucotrichum and of none of M. cinctum, produced a cytotoxic reaction in tissue-culture cells of the type which was correlated with mammalian toxicity. Toxic isolates were most frequently recovered from irrigated pasture, but populations in the pastures examined were apparently too small to cause disease in grazing animals.