Evaluation of the Nematicidal and Phytotoxic Potential of Ricinus communis, Cosmos bipinnatus, and Tagetes erecta Plant Extracts in Tomato

Plant-parasitic nematodes cause great damage to tomato production, which consequently has a deleterious economic impact on producers. For decades, parasitic control has relied on chemical nematicides with toxic environmental effects. Currently, an emerging option is the use of plant extracts, which offer suitable control of these plant pathogens without causing environmental damage. Therefore, in this study we examine the activity of three plant extracts to reduce the population of plant-parasitic nematodes that cause root gall formation in tomato plants, using in vitro tests and greenhouse experiments. First, a molecular identification of the nematodes was performed, identifying the pathogen species as Meloidogyne incognita and Nacobbus aberrans. Then, different extract concentrations were obtained from plant tissues of Cosmos bipinnatus, Ricinus communis, and Tagetes erecta. It was found that C. bipinnatus extract presented the highest nematode immobility, followed by T. erecta, reducing populations by up to 95 to 100%. Nevertheless, according to the germination tests on tomato seeds, the extracts also seem to have a minimal phytotoxic effect on the development/first growth stage of tomato plants under greenhouse conditions.