Dry rot on swedes and turnips causes considerable crop losses throughout New Zealand. Cunningham (1927c) reviewed the history and importance of the disease; he demonstrated that it was both soil and seed borne. Cruickshank and Palmer (1954) summarised work on resistance to this disease in varieties grown in New Zealand. Lloyd (1959) noted that viability of the fungus in seeds deteriorated after eight months but was still present in a few seeds within a sample after 14 months. Smith (1956b) showed that a perithecial stage typical of Leptosphaeria was associated with the dry rot fungus; he therefore stressed the importance of air-borne ascospores in disseminating the disease within a crop. Smith and Sutton (1964) showed that this ascospore form was, in fact, identical with Leptosphaeria maculans.