PATH 372 Diseases of Horticultural Crops

7) Root knot nematode – Meloidogyne sp.
Root knot is the most important group of phytonematodes and was first recorded in
green house vegetables in England in the year 1855. Of the four predominant species
of Meloidogyne, M. incognita and M. javanica are commonly found in the tropics,
whereas M. arenaria is more common in the sub-tropics. M. hapla is common in the
temperate region and can occasionally found in the cooler uplands of tropics.
Symptoms
Formation of galls on host root system is the primary symptom
Roots branch profusely starting from the gall tissue causing a ‘beard root’
symptom
In severely infected plants the root system is reduced and the rootlets are almost
completely absent. The roots are seriously hampered in their function of uptake
and transport of water and nutrients
Plants wilt during the hot part of day, especially under dry conditions and are often
stunted.
Seedlings infected in nursery do not normally survive transplanting and those
surviving have reduced flowering and fruit production
Mode of spread and Survival
Juveniles and eggs survive periods of moisture stress in a state of anhydrobiosis
Irrigation water and soil adhering to animal feet and implements help in
dissemination of juveniles and eggs of nematodes
Management
Crop rotation with graminaceous hosts
Inclusion of non-preferred hosts like mustard, sesame, maize, wheat, etc., in the
cropping system
Intercropping of marigold with tomato reduces nematode population
Nursery should be raised in nematode free sites or fumigated beds
Deep ploughing of infested fields during summer. Three summer ploughings at 10
days interval reduces juvenile population
Flooding the field for prolonged periods
Use of biocontrol agents like Paecilomyces lilacinus (egg parasite)
Nursery bed treatment with metham sodium (Vapam)@25ml/m 2 or
Carbofuran@0.39g a.i/m 2
Bare root dip treatment in EC formulation of systemic pesticides like Dimethoate
or Phenemiphos for 6-8 hours before transplantation
Grow resistant varieties like Hissar Lalit and PNR-7
Integration of three summer ploughings or use of treated nursery with spot
application of carbofuran @1 kg a.i/ha at transplanting stage have been found
successful to manage nematode population in tomato.
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