However, if parsnips are to be grown in the same bed twice during a year, all leaf trash and especially all cankered roots should be removed from the bed and destroyed. Powdery mildew causes a powdery white appearance of the leaves, especially when plants are watered in the evening. Products containing sulphur are registered for the control of powdery mildew in vegetables. Pests Root knot nematode and other nematode species may be serious problems. Two spotted mite is a major pest of parsnips, especially from February to June.
Infested foliage looks unhealthy and mottled.
They are visible to the naked eye and are recognised by a dark spot on either side of the back. Weevils and black beetles may cause problems to the roots. Use chlorpyrifos to control weevils. Disorders Parsnips are often seriously affected at any time of the year by an orange discolouration on the roots. The cause is not known.