The distribution and importance of annual ryegrass toxicity in Western Australia and its occurrence in relation to cropping rotations and cultural practices

Abstract

Surveys in Western Australia showed annual ryegrass toxicity to occur on 152 farms in an area around Gnowangerup measuring c. 100 km by 150 km and on 18 farms in four other isolated areas. The disease has spread rapidly during the last 10 years, and has been favoured by practices aimed at pasture improvement in alternating crop-pasture rotations. In the last four seasons, between 76 and 95 % of all stock mortalities due to ryegrass toxicity occurred on fields grazed in the season following a cropping year. Under these conditions, ryegrass is dominant in the pasture, and infection levels are highest. Burning these fields in autumn reduces the level of infection and makes the pasture relatively safe to graze in this season.