Parsnip Diseases and Pests

The Most Common Diseases of Parsnips

The parsnip is a root vegetable from the umbellifer family, closely related to the carrot. That’s why it can potentially be affected by the same diseases as the carrot. Let’s take a look at the different diseases with their symptoms, and most importantly, the natural treatments and preventive measures to implement.

Alternaria Leaf Blight

In parsnips, this disease is caused by the fungus Alternaria dauci which thrives in humid weather, between April and October. The spores of these fungi can survive in the soil for 6 to 7 years, overwinter on the leaves, or be spread by seeds.

Symptoms of Alternaria Leaf Blight on carrot leaves

Symptoms: the foliage turns brown then black at the edges, then dries or rots. Young plants die. Some roots may be marked with superficial spots that can lead to rot during storage.

Direct control: in case of a severe attack, treatment with Bordeaux mixture can be applied as soon as the disease appears. Otherwise, it is absolutely necessary to remove and destroy affected plants which should not be composted.

Prevention:

• Apply a crop rotation of at least 4 years
• Avoid using fresh organic manure
• Avoid dense sowing
• Destroy plant residues after harvest
• If weather conditions combine humidity and heat, perform preventive spraying of horsetail decoction or garlic every 3 days for 10 days.

Powdery Mildew

Powdery mildew in parsnips is caused by a specific fungus Erysiphe. It generally develops in dry and hot weather. The spores are dispersed at the end of summer by the wind and it overwinters on plants and plant debris. The disease appears at the end of the vegetative period.

Symptoms of powdery mildew on cucumber foliage

Symptoms: small white, dusty-looking spots appear on the leaves. As the disease progresses, the foliage turns grey, covering both the upper and lower surfaces and becomes necrotic.

Direct control: spray with horsetail decoction.

Prevention:

• Avoid fertilizers too rich in nitrogen
• Avoid dense sowing and ensure good air circulation around the sowing
• Collect plant debris
• Remove contaminated plants
• Keep the soil well moistened

Fusarium Wilt

This disease is caused by the fungus Fusarium avenaceum which can remain in the soil for many years. The disease is also transmitted by seeds. It develops in warm and humid weather.

Symptoms: often, a type of dry mould appears around the collar of the parsnips. The affected parts brown and wilt, then dry and harden.

Direct control: it is absolutely necessary to pull up and destroy affected plants, and possibly replace the soil around the roots.

Prevention:

• Sow early and promote rapid germination by keeping the soil well moistened
• Practice a crop rotation of at least 3 to 4 years
• Thoroughly work the soil beforehand and add compost to introduce new fungi that compete with Fusarium
• Use uncontaminated seeds.

Various Rots

The roots of parsnips can be affected by various rots: grey rot caused by the fungus Botrytis cinerea, white rot due to Sclerotinia, and root rot caused by Phytophtora sp. These fungi mainly develop in humid years. Grey rot is characterized by a grey felting on the affected organs, white rot develops on stored parsnips, and root rot is indicated by brown to black bands on the roots, visible after harvest.

It all comes down to prevention:

• Ensure good soil drainage and avoid sprinkler watering
• Improve soil fertilization with compost additions
• Maintain a crop rotation of at least 3 years
• Clean gardening tools thoroughly
• Carefully inspect parsnips before storing and eliminate any that show signs of suspicion.

Parsnip Canker

Parsnip canker, caused by the fungus Itersonilia, can cause significant damage. It may come from contaminated seeds, but the fungus also overwinters in the soil. Spores are dispersed in the spring by the wind and affect the foliage. Then, they fall to the ground and attack the roots. Cool and humid weather conditions facilitate the development of the fungus.

Symptoms: small orange lesions, surrounded by green, appear on the foliage, grey to black lesions develop at the base of the petioles. Brownish-red, then black cankers develop on the collar.

Preventive control:

• Use resistant varieties such as ‘Tender and True’
• Hill up parsnips to well cover the shoulder of the roots
• Maintain long crop rotations of at least 3 years
• Work the soils well to drain and aerate them
• Prevent weeds from developing
• Eliminate all suspect parsnips during harvest.

The Main Pests of Parsnips

Four pests can potentially attack parsnips: the carrot fly, a beetle named Phytoecia icterica, wireworms, and aphids, the latter being not very harmful. However, I invite you to discover how to get rid of them: Aphids: Identification and Treatment.

Wireworms, also known as “wireworms,” can parasitize parsnip roots and significantly damage the harvest. Again, to learn all about this pest, I invite you to read Olivier’s article: Wireworm: Damage, Treatment, and Organic Control.

Wireworms can cause severe damage to parsnip roots

As for the carrot fly (Psila rosae syn Chamaepsila rosae), it is also a concern for parsnips. It is the larvae that burrow into the roots. The key is to protect against them, as once established, the larvae cannot be dislodged. Ingrid B. shares her prevention solutions: Carrot Fly, Leek Moth: Protect Your Crops!

Then there’s the small beetle Phytoecia icterica, otherwise known as the butcher’s needle. This beetle lays its eggs in the soil, near the roots of parsnips. The larvae enter and burrow into them, causing them to rot. This beetle is more prevalent in southern departments, in cool and moist areas. Its life cycle spans two years. The larvae overwinter in the form of a chrysalis on plant residues.

Preventive Control:

• Remove plant residues after harvest
• Install thick mulch on the soil during the adult activity period from April to July.