Managing the Phytotoxicity and Inconsistent Nematode Suppression in Soil Amended with Phytonematicides

Abstract

High incidence of phytotoxicity and inconsistent results in nematode suppression of soil amended with phytonematicides had been limiting the adoption of phytonematicides in various countries. The efficacy of phytonematicides depended on allelochemicals as active ingredients, which are naturally phytotoxic. Plant species respond to increasing concentrations of allelochemicals through density-dependent growth patterns, which have three phases, namely, stimulation, neutral and inhibition, with each phase having a range of concentrations. The curve-fitting allelochemical response dosage model was used for two triterpenoid phytonematicides, nemarioc-AL and nemafric-BL phytonematicides, to develop the non-phytotoxic concentrations of the products within the stimulation phase of tomato (Solanum lycopersicum) plants. The concept called for the development of the application interval, culminating in the formulation of the application frequency and the dosage, which ameliorated the incidence of phytotoxicity. The application intervals of the derived non-phytotoxic concentrations for the products were such that the life cycle of the root-knot (Meloidogyne species) nematodes was continuously disrupted, thereby ensuring consistent results in nematode suppression in soils amended with phytonematicides.