Biological Control of Typhula isikariensis on Perennial Ryegrass.

Abstract

Low-temperature fungi were collected from plants just after snowmelt, and their antagonistic activity against Typhula ishikariensis, a snow mold fungus, was determined using orchardgrass seedlings. Isolates from gramineous plant debris, considered to beT. phacorrhiza, suppressed the disease caused by T. ishikariensis biotype A or B. Antagonists differed in their effectiveness against these biotypes. Isolates antagonistic to biotype A, which is the principal snow mold of perennial ryegrass in northern Hokkaido, were localized in this district. Despite prolonged snow, susceptible, perennial ryegrass is successfully grown there. These findings suggest the natural occurrence of biological control of the disease in perennial ryegrass pastures in northern Hokkaido. Ground tissues of orchardgrass or alfalfa reduced activities of antagonists when mixed in the inoculum. Plant litter such as fallen maple leaves and rice straw favored antagonism. Application of the antagonists in a naturally infested field planted with perennial ryegrass resulted in an yield increase of 26.5% compared with the untreated control where fall cutting favored the occurrence of snow mold. Where plants were not cut in fall and snow mold damage was slight, yield increase was insignificant.