Studies on parsnip canker

SUMMARY Cankers of parsnips growing in the East Anglian fens were caused by a species of Centrospora . Comparison of the morphology and pathogenicity of isolates from infected roots with those of isolates from carrot and celery and also with published information, indicated that the fungus from parsnips was C. acerina . One of the parsnip isolates saltated to give sectors resembling a culture received from the Centraalbureau voor Schimmelcultures, Baarn as C. macrospora , confirming that, as reported previously, this fungus is a form of C. acerina . The foliage of a wide range of seedling hosts was susceptible to artificial infection. In a laboratory test, wounding of parsnip roots before inoculation with Centrospora did not increase lesion development. Lines of parsnip bred for resistance to Itersonilia and Phoma were also resistant to attack by Centrospora . In view of the susceptibility of parsnips, carrots and celery to infection by C. acerina , adequate rotation on fen soils, where these crops are frequently grown, is advisable.