South African plants with nematicidal activity against root-knot nematodes: A review

Research on using plants as control agents for plant-parasitic nematodes has received substantial attention due to the ability of plant-derived extracts and compounds to either paralyze or kill nematodes. Nematicidal properties of certain plants have been tested in vitro and in vivo using glasshouse and field trials, either using powdered meal (plant material) or extracts by incorporating them as soil amendments or as seed treatments. The present review aims to document South African plants used for controlling root-knot nematodes, i.e. Meloidogyne spp., summarizing in vitro and in vivo results of experiments conducted to assess their efficacy. Several databases were mined to obtain information on plant use as organic amendments for controlling Meloidogyne infections in South Africa. Inclusion criteria focused on plants as organic amendments and the use of plants against Meloidogyne infection. Meloidogyne incognita race 1 and race 2 are the most commonly studied nematodes infecting tomatoes, which are highly susceptible to nematode infection. Seventeen plant species were reported to effectively reduce the population density of nematodes in the soil in glasshouse, microplot and field trials. The in vitro experiments are generally used as guides for investigating if activity occurs via mortality or egg hatchability. Further research exploring South African plants as control agents for root-knot nematodes, chemicals responsible for activity and the plants’ mode of action is warranted.