SURVIVAL IN SOIL OF ITERSONILIA PASTINACAE CHANNON CAUSE OF PARSNIP CANKER

When parsnip roots, naturally infected with Itersonilia pastinacae Channon, were buried in the field, the fungus was still viable after 12 months. When the stem apical meristems of the roots were removed to promote their more rapid decomposition, the fungus did not survive burial longer than 7 months. In laboratory experiments using pieces of fiber-glass mesh impregnated with I. pastinacae, the fungus remained viable after 12 months burial in sterile soil, whereas it was not viable in natural soil after 7 months. In natural soil marked lysis of the mycelium of the fungus occurred in 2 weeks, leaving intact the more resistant chlamydospores. Ballistospores, the air-borne stage of I. pastinacae, could not be recovered 2 days after being added to natural soil, whereas the recovery rate from sterile soil was high after 5 days. Isolates of Bacillus subtilis and Streptomyces spp. from natural soil were shown to be antagonistic to I. pastinacae.