An ecological study of pasmo disease (Mycosphaerella linorum) On linseed in Canterbury and Otago

Abstract

Abstract Pasmo, caused by the fungus Mycosphaerella linorum, is one of the commoner diseases of linseed in New Zealand, and occasionally causes severe losses. The most recent was during the 1960-1 season. Laboratory tests and field trials during the following season showed that seed transmission, though possible, was a minor factor. Infected cotyledons were found in one commerciai crop only. From mid-January_1962, however, the incidence of the disease steadily increased, until by harvest it had become general. The probable sources of infection were Australian flax (Linum marginale) growing on the roadsides, and litter remaining Irom the previous linseed crops. The fungus was isolated from both sources, and cross inoculations between linseed and Australian flax were successful. Both in the Ashburton crops and in all plots grown in the Dunedin district, the disease was evenly distributed, which suggests that the infection arose from wind-blown spores picked up over a large area. The disseminants were probab...