Effects of new-generation nematicides on nematode assemblages in soybean rhizospheres

Abstract

The root-knot nematode (Meloidogyne spp.) is known to cause severe yield losses in agricultural crops, especially in soybean. The number of nematicides available in the current market is reducing while the environmental impacts of these nematicides have proven to be harmful. Research to identify effective biological control agents of nematodes is becoming increasingly important while introducing new-generation nematicides can reduce the environmental impacts. In this study, the effect of new-generation nematicides was evaluated in both in vitro and in vivo experiments. In vitro bioassays were conducted using eight different biological products (T3C, Oligo, Ses-A, Aba-5, Graphite, BM-T, Green liquid, and Oxa-40). The most effective products were then evaluated in a micro-plot experiment, together with DT-200, RV42-20, a commercial fertilizer (Bio-Green) and a commercial nematicide (Velum® 1GR). Tunnel as well as field experiments were also conducted to evaluate the reduction of root-knot nematode populations under natural conditions, using the commercial fertilizer (Bio-Green and the commercial nematicide Velum® 1GR). The most effective new-generation nematicide in the in vitro trial was the Oligo-product. However, all the evaluated products significantly reduced the motility of J2 Meloidogyne spp. The micro-plot experiments resulted in no significant differences between the nematode population densities of the different treatments after 112 days after emergence (DAE). Both the tunnel and field trials of the commercial products, Velum® 1GR and Bio-Green granule significantly reduced nematode densities, while a combination of both the products had the most significant reduction in nematode population densities after 112 DAE. In conclusion, new-generation nematicides have the potential to reduce root-knot nematode population densities. However, natural conditions influence the effectiveness of these nematicides, and further studies should be conducted to improve the efficacy of these products during different environmental conditions and for a variety of crops.