Meloidogyne spp.

root-knot nematodes

General

• Worldwide widespread and extremely polyphagous, they are by far the most frequent and most damaging nematodes on tropical vegetables; their damage is sometimes considerable in farms where the management of crop rotations and the sanitary quality of the soil are not good.
• Several species of Meloidogyne on vegetables mainly causing root galls ( Meloidogyne incognita (Kofoid & White) Chitwood (the most widespread species), Meloidogyne arenaria (Neal) Chitwood, Meloidogyne javanic a (Treub) Chitwood and Meloidogyne hapla Chitwood (most common species Other species have been reported more occasionally: Meloidogyne chitwoodi Golden et al., Meloidogyne floridensis Handoo, Meloidogyne ethiopica Whitehaed, Meloidogyne acronea Coetzee, Meloidogyne mino r Karsen, Meloidogyne mayaguensis Rammah & Hirschmann. recent, has been described on the American continent and in Africa.
• Some isolates are able to overcome the resistance conferred in tomato and some rootstocks by the “ Mi ” gene (notably in M. incognita, M. arenaria and M. javanica ).
• Extremely polyphagous and attack many plants, cultivated or not (more than 5500 plants), on which they ensure their multiplication and their conservation (pepper, eggplant, tomato, lettuce, melon, cucumber, zucchini, carrot, celery, bean, potato sweet, banana, etc.).
• Observed both in the open field and under shelter.

• Susceptible botanical family(s):

Biology

 Preservation : keeps for several years in the ground in the form of masses of eggs protected by a mucilaginous gangue, but also thanks to a large number of plants, whether cultivated or not, which ensure their multiplication and conservation.

• Parasitism : The larvae penetrate the roots and migrate to the vessels through the cortex, between the cells. Induce galls surrounding large pear-shaped females which produce numerous eggs (300 to 3000, between 400 and 500 on average).
• Dissemination : Passive of eggs and larvae by runoff, drainage and irrigation water. Larvae actively move short distances in moist soils. Dissemination is possible via soil dust, contaminated plants, tillage tools and agricultural machinery.
• Favorable conditions : active in hot and humid soils, their activity seems to be greatly reduced, even blocked below 5°C and above 38°C. Soil inoculum density, the influence of various stresses on plants (compacted or low humidity soil, nutritional deficiency, attacks by various pests, etc.) also influence nematode attacks and the severity of their damage.

Protection

• Listing rotations (soja, oignon, ail, mais, arachis, Paspalum notatum, Cynodon dactylon, Eragrostis curvula, Chloris gayana, Digitaria decumbens, Panicum maximum, Crotalaria spp., Mucuna pruriens , sésame, etc.)
• Disinfect the soil by solarization or biodisinfection .
• Immersion of infested plots for several months would help reduce soil population levels.
• Bury in the ground just before planting certain composts or green manures (coffee pulp, cakes based on Azadirachta indica, Chrysanthemum coronarium, Ricinus communis, Sorghum sudanense , etc.).
• Cultivate the soil superficially during the dry season to expose the nematodes to the effects of the sun.
• Thoroughly clean the tools and equipment used for working the soil in contaminated plots before using them in healthy plots. Thorough rinsing with water is often sufficient.
• Trap plants and/or nematicides ( Tagetes spp.), microorganisms , parasitic and nematicidal
• Use varieties or rootstocks if they exist (mainly in Solanaceae).
• Transplanting into larger clods will in particular delay infestations.
• Control the sanitary quality of the plants, avoid planting contaminated ones.
• Eliminate weeds gradually by working the soil superficially at regular intervals.
• Water the plants during the hottest periods of the day to prevent or even reduce wilting.
• Mound the plants to promote the development of adventitious roots.
• Eliminate as much as possible the root systems of the plants attacked and destroy them in order to avoid enriching the soil with nematodes. Otherwise, the roots will be put in the open air so that they suffer the effects of the sun.
• Composting does not completely eliminate nematodes from plant debris.
• Some nematicide  can be used against nematodes.