FUNGAL AND VIRAL DISEASES LIMITING PRODUCTIVITY OF ANNUAL PASTURE LEGUMES IN A MEDITERRANEAN-TYPE ENVIRONMENT

M.J. Barbetti ¹²³ and R.A.C. Jones¹²

¹Centre for Legumes in Mediterranean Agriculture, The University of Western

Australia, Nedlands, 6907, Western Australia

² Agriculture Western Australia, Locked Bag No.4, Bentley Delivery Centre, Bentley, 6983, Western Australia

³ Faculty of Agriculture, The University of Western Australia, Nedlands, 6907, Western Australia

Fungal and viral diseases seriously affect the productivity of annual pastures in south-west Australia which has a Mediterranean-type climate.  The predominant legume components of these pastures are either subterranean clover or annual medics.  The major fungal diseases of subterranean clover are root rots, Northern anthracnose (known in Australia as clover scorch; caused by Kabatiella caulivora), rust (Uromyces trifolii), and Cercospora leaf spot (Cercospora zebrina). Its major viral diseases are caused by bean yellow mosaic and subterranean clover mottle viruses.  In medic, Phoma black stem and leaf spot disease (Phoma medicaginis), fungal root rots and disease caused by alfalfa mosaic virus are the most important.  Substantial losses in herbage and seed yields result from these diseases both in grazed and ungrazed monoculture swards and in grazed regenerated, mixed species swards. Integrated approaches to disease control involve sowing disease tested seed, altering the species mix within the pasture, modified cultivation, grazing and rotational measures, application of fungicides or insecticides, and use of disease-resistant cultivars.  For the long term, the best prospect for economic control lies in natural or genetically engineered host resistance.

Keywords: legumes; diseases; fungus; virus; decline; losses; productivity; pastures.