Compatibility of methanolic extract fractions of Citrus sinensis pomace with biological agents for managing the root-knot nematode Meloidogyne javanica in soybean

Agroindustrial wastes are increasingly investigated for phytonematode management due to their rich phytochemical composition. However, they may also affect beneficial microorganisms used as biological control agents. This study evaluated the effects of extract fractions from Citrus sinensis (L.) Osbeck pomace, alone or combined with nematicidal agents, on the reproduction of Meloidogyne javanica (Treub, 1885) Chitwood in soybean, and assessed in vitro compatibility with biological agents and egg parasitism. A greenhouse reproduction assay used commercial products based on Purpureocillium lilacinum (Thom) Luangsa-ard, Houbraken, Hywel-Jones and Samson + Pochonia chlamydosporia (Goddard) Zare and Gams, Bacillus firmus Bredemann and Werner, and abamectin, applied with or without the ethyl acetate (EAF) and dichloromethane (DCMF) fractions of a crude methanolic extract prepared at 1.5% (m/v), plus an untreated control. For microbial growth, microorganisms were isolated from the commercial products and cultured in the presence or absence of EAF and DCMF. Egg parasitism was evaluated by incubating M. javanica eggs with nematophagous fungi with and without the fractions. EAF and DCMF alone reduced M. javanica reproduction in soybean and did not alter the efficacy of the nematicidal agents. Conversely, the fractions, particularly EAF, reduced mycelial growth and sporulation of P. chlamydosporia and P. lilacinum and decreased B. firmus viability, and their combination with the fungal treatment reduced egg parasitism. Nevertheless, when applied in combination with nematicides, extract fractions did not influence the control of M. javanica in soybean.