"Trying to find a cure for parsnip canker."

According to the National Vegetable Society, parsnip canker is disease which causes the parsnip to blacken around the top and work its way down the vegetable rendering it  unusable. One of the various fungi that can cause the disease is Itersonilia pastinaceae which is found in the soil. The disease usually occurs in autumn and, according to Down Gardening Services, " sowing later to avoid root fly damage and earthing up to prevent spores washed down from the foliage are two measures which can be taken to reduce the problem."

From Down Garden Services

From National Vegetable Society