Monitoring the toxicity of lupin (Lupinus angustifolius) stubbles has limited value in the prevention of lupinosis

Abstract

Lupin (Lupinus angustifolius) stubbles at 3 'sentinel' sites in the Midlands Region of Western Australia were monitored throughout the summer of 1985-86 to assess the level of infection of the stems by the fungus Phomopsis leptostromiformis, and to measure the concentration of its toxic product, phomopsin A. These parameters were found to have little value as predictors of fungal infection and of the toxicity of lupin stubbles on farms in surrounding districts. It was found also that visual rating of the level of P. leptostromiforrnis infection of lupin stems was unrelated to the concentration of phomopsin A in those stems or to the liver damage in sheep grazing stubble from which the stems were sampled. It is suggested that these ratings should not be used to advise farmers on the 'lupinosis risk' of a lupin stubble. Monitoring the phomopsin A concentration in lupin stems collected throughout a summer confirmed that rain, associated with cloudy days, was the primary environmental stimulus to a significant increase in the phomopsin A concentration.