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Nematodes are soil inhabitants of cosmopolitan distribution. Although different species of nematodes have been reported to infect lentils, on which they might cause serious damage, information on them is still scanty. Also, the relative importance of particular species has to be considered if resistant cultivars are to be developed. The information on four nematodes affecting lentil is presented here. Common practical control methods are mentioned at the end.
Root-knot nematode
The disease is caused by Meloidogyne spp. At maturity, the female nematode becomes swollen and pearly white, producing an egg sac that often protrudes posteriorly to the exterior of the gall. The sac becomes brown and may contain several hundred eggs. Eggs hatch without requiring host diffusate; the second stage larvae invade roots and migrate to the site of differentiating vascular tissues where they feed and cause the development of several giant cells around the nematode head. This leads to the formation of galls.
Symptoms: The most characteristic feature of the infected plant is the presence of root galls (Fig. 30), out of which small lateral rootlets usually develop.
Although galls have some resemblance to nodules of nitrogen-fixing bacteria, they are easily distinguished from them. Galls are usually not colored and they cause swelling of the root diameter. Heavily affected plants are stunted and die, causing a sparse plant stand (Fig. 31).
In old infections, roots are usually rotted because of attack by secondary root-rotting microorganisms.
Root lesion nematode
Root lesion nematodes also are cosmopolitan in distribution. They attack a wide range of cultivated crops and weed plants and have been reported to infect lentil in Syria.
The disease is caused by Pratylenchus spp. Both larval and adult forms enter roots and feed on the cell contents. The life cycle is completed within a month. Nematodes overwinter in the soil and within root tissues.
Symptoms: The infected plants are stunted and often yellow. The nematode feeding generally causes the formation of dark, elongated, water-soaked or cloudy yellow lesions and overall browning. The lesions mainly appear on the young feeder roots and are most concentrated in the area of root hairs.
Further discoloration and rotting of the affected root areas might occur because of infection by secondary fungi and bacteria.
Extensive feeding may decrease nodulation and result in dramatic yield reduction and killing of plants.
Other nematodes
Stem nematode (Ditylenchus sp.) and cyst nematode (Heterodera sp.) have been isolated from lentils in Syria.
Control: Use a long crop rotation, which helps to keep nematode populations at low levels and avoid serious damage to crops.
Fall plowing to expose nematodes to low temperatures may help in reducing the high infection.
Use of resistant lines is not possible as they are not yet available.
Use of nematicides to control lentil nematodes is not economical.
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