Control of root-knot nematodes by a mixture of maleic acid and copper sulfate

Abstract Organic acids released during the decomposition of organic soil amendments have been used in crop fields as benign chemicals to control phytopathogens. However, the use of organic acids against root-knot nematodes (RKNs, Meloidogyne spp.) has not been recommended in practice, owing to their short retention time in the soil. In this study, we tested the nematicidal activity of organic acids including maleic, fumaric, acetic, acrylic, caprylic, oxalic, and formic acids, as well as copper sulfate against Meloidogyne incognita . Maleic acid showed the strongest nematicidal activity with induction of 100% second-stage juvenile (J2) mortality and 70.47% hatching inhibition at a concentration of 0.37 mmol/L. In addition, the combination of maleic acid and copper sulfate was revealed to have an additive effect in J2 mortality. Application of a wettable powder-type formulation of a mixture of maleic acid and copper sulfate (MIX-WP30) reduced RKN disease on tomato by 51.72% in a pot experiment, suppressed gall formation on melon and decreased nematode population density in the soil. Under field conditions, the efficacy of MIX-WP30 (46.73%) was comparable with that of the commercial nematicide fosthiazate (48.38%). This study identified the effectiveness of MIX-WP30 against RKNs, and demonstrated that there was an in vivo synergistic effect of MIX-WP30. Based on its nematicidal activity, MIX-WP30 could be used as an effective nematicide for RKN management.