Abstract

Pyrenophora semeniperda (anamorph Drechslera campanulata) causes a minor leaf spot and seed infection of at least 36 genera of annual or perennial grasses and has been recorded on several dicotyledonous species. The fungus causes distinctive 'ring spot' leaf lesions, 1–4 mm in size with a light-coloured centre and dark-brown margin. It also produces prominent black stromata up to several centimetres long from germinating seeds. Thus, although it is a relatively uncommon fungus, it is unlikely to be overlooked. The current world distribution is in temperate grasslands and cereal growing areas of Argentina, Australia, Canada, Egypt, New Zealand, South Africa and the United States of America: there are no definite records from Europe or Asia. Reports of its epidemiology are reviewed to show that the fungus is unlikely to be more than a minor leaf and seed disease. It is readily seed-borne on a wide range of cereals and grasses that are traded internationally, so there have been many opportunities for it to spread beyond the limits of its natural distribution. There are no reports of economic losses associated with P. semeniperda. Although the pathogen produces highly toxic compounds, there have been no definitive reports of ill health in animals that have grazed pastures with natural levels of leaf infection of P. semeniperda.