The developing relationship between Stylosanthes and anthracnose after 14 years in a North Queensland pasture. 1. Field study

Abstract

A 28.5 ha pasture sown in 1975 with a mixture of 7 different accessions of Stylosanthes provided information on anthracnose epidemics (caused by Colletotrichunz gloeosporioides) occurring under grazing in 1987 and 1989. The disease incidence varied throughout the area in response to the density patterns of Stylosanthes with dense populations recording more anthracnose than sections where there were fewer plants. Non-host pasture components did not influence disease incidence. The disease was present on 32% of the plants in the 1987 survey and on 65% of plants in 1989. This probably reflected different stages of epidemic development rather than an overall increase in epidemic severity. Several accessions which were sown in 1975 were not found in significant numbers, and the contribution of anthracnose to their demise is not known; however, in addition to the sown accessions, plants appearing to be S. scabra x S. hamata hybrids were commonly observed. The incidence of anthracnose on these largely infertile plants was not high. The pasture, 14 years after establishment, has persisted with a large host population sustaining varying amounts of anthracnose.