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Damage to vegetables caused by root-knot nematodes

Damage to vegetables caused by root-knot nematodes

Plant-parasitic nematodes are of considerable importance across the agricultural industry worldwide and their devastating effects on crops have major economic and social impacts. About 27,000 species of nematodes have been formally identified.

Among plant-parasitic nematodes, Meloidogyne spp. or root-knot nematodes have the greatest economic impact on crops worldwide. These nematodes can parasitise nearly every plant species, resulting in devastating adverse effects on the quality and yield of host crops.

Typically, root-knot nematodes reproduce and feed within plant roots and induce galls or ‘root-knots’. Nematode damage symptoms are most noticeable at high levels of infestation. However, plant-parasitic nematodes often produce symptoms on above ground plant parts which are assumed to be a nutritional deficiency, disease or even a lack of water. For this reason, many infestations can go unrecorded and allow serious problems develop over time.

Infective root-knot nematode juveniles hatch from eggs when conditions are favourable, and are mostly attracted to host roots due to exudates. Following root invasion, host plants react to feeding by root-knot nematode juveniles and undergo physiological changes. Induced feeding sites for the root-knot nematode, or nurse cells, are established. In addition to these highly specialised cellular adaptations, root tissues around the nematode undergo hyperplasia and hypertrophy causing the characteristic root gall usually associated with Meloidogyne infestations.

The impact of root-knot nematodes on roots of host plants is characteristic, with large galls usually visible on plant roots. These galls affect the ability of the plant to uptake nutrients and water, resulting in above-ground symptoms such as suppressed shoot growth; nutritional deficiencies showing in the foliage, particularly chlorosis; temporary wilting during periods of mild water stress and suppressed plant yields.

Selected root-knot nematode species that have been reported causing economic damage to vegetable crops in the UK are:

  • Meloidogyne hapla – The ‘northern root-knot nematode’. Recorded parasitising onion, radish, beets, cabbage and other brassicas, carrots, parsnips, peas and beans.
  • Meloidogyne naasi – Found principally on cereals and grasses, however it has been recorded on vegetable hosts such as beets, onion peas and beans.
  • Meloidogyne artiellia – Reported to infest cabbage and other brassicas, radish and beans. In general this nematode induces very small galls, sometimes with lateral root proliferation.
  • Meloidogyne minor – A recently described species, found principally on grasses but has been shown to parasitize carrot under experimental conditions.

Effective management of plant-parasitic nematodes in soils should be based on accurate detection and identification, to understand the biology and host range of each species in the population.

To address this challenge Fera has established the Fera Plant Clinic. It provides a unique free-living nematode identification service, and offers nematode detection and consultancy advice for all sectors of agriculture and horticulture.

For further information contact, call the Fera Plant Clinic helpline on 01904 462324 or visit