Root-knot Nematode (Meloidogyne spp.) – Symptoms, Damage and Preventive Measures

January 27, 2023April 11, 2024 Agric4Profits

Root-knot Nematode (Meloidogyne spp.) affects all species. This is a microscopic soil worm living in hot, humid and airy soils that penetrates roots and causes growth decrease and plant death. It also enables other noxious soil organisms to enter in the plant.

Root-knot nematodes are plant-parasitic nematodes from the genus Meloidogyne. They exist in soil in areas with hot climates or short winters. About 2000 plants worldwide are susceptible to infection by root-knot nematodes and they cause approximately 5% of global crop loss.

Root-knot nematode larvae infect plant roots, causing the development of root-knot galls that drain the plant’s photosynthate and nutrients. Infection of young plants may be lethal, while infection of mature plants causes decreased yield.

Meloidogyne incognita, also known as the “southern root-nematode” or “cotton root-knot nematode” is a plant-parasitic roundworm in the family Heteroderidae. This nematode is one of the four commonest species worldwide and has numerous hosts.

Root-knot nematodes (Meloidogyne spp.) attack the roots of various trees, shrubs and herbaceous plants. Infested roots become distorted and develop rounded or irregular galls.

These galls measure anything from 1 to 20 mm across and often coalesce, causing considerable distortion. The nematodes also exacerbate the deleterious effects of pathogenic bacteria and fungi.

Root-knot nematodes are associated mainly with light soils but most damage is caused under glass, particularly in hot conditions where certain tropical and subtropical species, e.g. the Javanese root-knot nematode (Meloidogyne javanica), have become established.

Pot plants such as Begonia, Coleus, Cyclamen, Gloxinia and various cacti may suffer considerable damage, severely affected plants appearing discoloured, lacking vigour and wilting under stress.

Northern root-knot nematode (Meloidogyne hapla) is a widely distributed, polyphagous pest in northern Europe; it attacks many different kinds of plant, including various ornamentals.

Root-knot nematodes invade host plants as second-stage juveniles; these settle down to feed in the young roots and usually reach maturity about 1–2 months later.

Adult females are translucent-whitish, pear-shaped and about 0.5-1.0 mm long. They may be found within the galled tissue, often attached to a gelatinous sac that contains masses of eggs.

In some cases development of the pest is parthenogenetic; in others, minute worm-like males mate with the females before eggs are laid.

First-stage juveniles develop within the eggs, second-stage individuals eventually breaking free and either migrating inside the root or escaping into the soil to commence feeding elsewhere.

These infective nematodes are capable of surviving in moist soil for about three months. In dry conditions they persist for no more than a few weeks.

Root knot Nematode Symptoms

Root systems of Medicago truncatula plants inoculated with Meloidogyne incognita. The plant on the left carries a gene conferring resistance to M. incognita , whereas the plant on the right is susceptible. Characteristic root knots (galls) are evident on the roots of the infected plant.

Root–knot nematodes can be identified to species using a number of techniques, but one common method is perineal pattern analysis. The perineum (the region surrounding the vulva and anus) of female nematodes displays a pattern of ridges and annulations for each species.

Some of the symptoms of this disease include the following:

Leaves yellowing and wilt from the bottom to the top.
Plant becomes more sensitive to drought.
There are lots of galls on roots.

Root-knot Nematode (Meloidogyne spp.) Damage Prevention

Some of the possible damage prevention measures include the following:

growing some other species less sensitive (sorghum, millet, corn, cabbage, onion, garlic, crotalania, peanuts plant).
Plant trap-plant like peanut plant before crop.
Field solarisation (Heat treatment).
Flood the plot.
Use manure in nursery.
Avoid to grow on an infected plot.
Dig up and let drying attacked plants.