Moulds on leaves of perennial ryegrass and white clover

Abstract

Moulds demonstrable by routine culture techniques on leaves of pasture plants were examined to assess the incidence of toxinogenic groups. Perennial ryegrass, white clover, and litter from ryegrass–dominant pasture were collected regularly for 2 years from sites in the Waikato basin. Numbers of moulds were highest on litter, lower on ryegrass leaves, and lowest on clover. Numbers were greater in paddocks being grazed than in those from which stock were excluded. The most commonly recovered groups were, in approximate order of frequency, pycnidial forms; Cephalosporium spp.; Cladosporium herbarum; Fusarium spp., in particular F. nivale’, Colletotrichum spp.; Rhyncosporium spp.; Verticillium spp.; Myrothecium spp.; Pithomyces chartarum, and Metar–rhizium anisopliae. F. nivale and two groups of Cephalosporium were virtually restricted to ryegrass leaves and litter, and Verticillium spp. and M. anisopliae to clover leaves; other groups were common to all types of substrate. The litter flora was qualitatively like that of green ryegrass leaves; that from some mixed pasture samples from Gisborne was similar to that from Waikato material.

Almost all moulds isolated belonged to taxa known to have some pathogenicity to plants; they did not appear to be true members of the phyllosphere. No evidence was found for succession of populations, each group apparently varying independently of the others. P. chartarum, F. nivale, and Myrothecium spp. were the most commonly occurring groups known to be toxic to mammals. P. chartarum made up about 1% of the moulds isolated during the first half of 1968, when there was a widespread outbreak of facial eczema.