How to identify and manage potato cyst nematodes

UK seasonality and monitoring

Potato cyst nematodes build over years where potatoes are grown repeatedly.

During this period inspect Potatoes and tomatoes, concentrating on the crop stage and plant parts described above. Note when and where fresh injury appears; old feeding marks can remain after the pest has moved on.

Crops and plants affected

The recorded hosts are Potatoes and tomatoes. This list identifies plants worth checking; it does not mean every crop is equally vulnerable. Start with the listed plants and inspect the tissue where this pest feeds.

Check affected crops for these signs: Stunted plants, yellowing and poor tuber yields in patches. Match the symptom to a live pest, larva, egg or characteristic feeding sign before deciding that treatment is needed.

Damage and likely consequences

Stunted plants, yellowing and poor tuber yields in patches. A small amount of old damage on a vigorous plant may be cosmetic. Continued feeding on roots, seedlings, growing points or edible parts can reduce establishment or yield.

On Potatoes and tomatoes, judge severity by checking whether injury is fresh and spreading, whether the plant is still growing, and whether the edible part is affected. Avoid removing a crop based on one ambiguous mark.

Prevention

Use clean seed potatoes and a long rotation; keep suspect soil on the affected bed and clean tools before moving elsewhere.

Control and integrated management

Seek recognised plant-health or horticultural advice about soil sampling and resistant varieties.

Natural predators and wildlife-conscious choices

Soil health and rotation are the key controls.

For potato cyst nematodes on Potatoes and tomatoes, use a barrier or hand removal only where it fits the crop and life stage. Keep any cover taut, inspect it for trapped wildlife, and remove it when protection is no longer needed.

Long-term management

Keep accurate potato and tomato bed records and follow specialist rotation advice if the nematode is confirmed.

For potato cyst nematodes on Potatoes and tomatoes, record the bed, crop stage and date when fresh damage first appears. Those notes help time protection and monitoring before the same crop stage is vulnerable next season.

Common mistakes

A symptom alone is not a diagnosis. These microscopic roundworms cannot be identified from leaves alone. Stunting in patches, poor roots and low yields are warning signs; confirmation requires a soil test because drought, nutrition and other root problems look similar. Look for a matching live pest or fresh feeding sign before intervening.

Patchy yellowing is a warning sign, not a diagnosis; do not move soil or tubers from a suspect bed.

If damage continues

Recheck Potatoes and tomatoes where new injury is appearing, including the hidden feeding site: roots, folded leaves, leaf undersides, flowers or fruit as appropriate. If identification remains uncertain, photograph a live specimen alongside the damage and ask an allotment association or horticultural adviser.

If the recommended control (Do not move infested soil; lift crops carefully and follow rotation advice.) has not helped, confirm that it was fitted or applied at the right crop stage and that fresh damage is still occurring. Old marks do not heal when the pest has gone.

Frequently asked questions