Identifying and Treating Parsnip Diseases

Parsnips (Pastinaca sativa) can be afflicted with parsnip diseases from a wide variety of causes, including fungi, phytoplasmas and bacteria. Some diseases are also transmitted by insect pests. Most of these diseases can be controlled by careful planting, crop rotation and soil management. Learn more about parsnip diseases and how to manage them from the tips provided here.

Fungi-Based Diseases

Root and Crown Rot: caused by three fungi, rhizoctonia, pythium and fusarium. The parsley plant will wilt and slowly collapse. The roots turn brown in color and appear waterlogged. Control this rot disease by rotating the parsnip crop every 2 years with corn or other grains.

Sore Head: cankers appear on the roots in the form of dark pits. The leaves can also become infected, with irregularly shaped spots that develop into lesions. Fungus spores from the leaves will then wash into the soil, infecting other parsnip roots. Rotate parsnips with other vegetable crops for up to 6 years, and keep the soil well-drained. Treat the leaves with a copper-formula fungicide to prevent the spread of fungus spores.

Leaf Spots: spots with sharp edges, yellow-green to dark brown in color, appear on the leaves. As these spots enlarge and join, the leaves will begin to drop off. Use a registered fungicide as allowed in your growing area to kill the fungus infection.

Bacterial Infections

Parsnip Blight: caused by the Pseudomonas bacterium. The root interior of the parsnip turns brown. Rotating crops out of parsnips for 2 years is the most effective control for parsnip blight

Phytoplasma-Based Diseases

Aster Yellows: also affects asters, carrots and lettuce. Plants produce excessive numbers of leaves. These are yellow and have a stunted shape. The roots do not increase in diameter and are covered with masses of slender root hairs. This disease is carried to parsnips and related plants by the leaf hopper. Eliminate leaf hoppers with approved insecticides. Do not plant parsnips near carrots or asters.

Insect-Borne Disease

Root-knot nematodes: cause small tissue knots on the main feeding roots, preventing the passage of nutrients from the soil to the leaves. Nematodes carry this disease to root vegetables such as parsnip and carrots. Rotate your parsnip plantings with plants such as corn that are not prey to this infection. As well, you should plant your parsnips in a new, uninfected area. Do not transport soil to the new planting site from the former site.

Insect Pests

Insects that afflict parsnip include aphids. These can be controlled with predator insects such as lady beetles and lacewings. Parsnip leafminers and parsnip webworms feed on the leaves and blossoms of the parsnip. Control by hand removal of the larvae is usually sufficient.

Preventing Disease and Infestation

Healthy parsnips, in well-watered and drained soil, will not generally fall prey to insect pests or diseases. Choose your planting locations carefully to prevent infection from tainted soil or diseased plants. Avoid mulching parsnip, so that air can get into the soil, and weed vigorously when the parsnip shoots are young, to provide the best conditions for their growth. Rotate parsnip out of its planting location every 2 years.