Harnessing the soil food web for the biological control of root-knot nematodes

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Many predatory mites are generalists and feed on a diverse diet, making them excellent candidates for conservation biological control programs. However, while their impact on above ground pests is frequently reported, only few studies have focused on below ground interactions of mites. The proposed project aims to harness the soil food web in agroecosystems, namely the trophic link between microorganisms, free-living nematodes (FLN) and predatory mites, for the biological control of root-knot nematodes (RKN). We hypothesise that FLN represent a high quality diet (e.g. due to nutritional valuable omega 3 fatty acids) for mites, enhancing predator fitness and in turn predation on RKN. These trophic interactions are investigated in four working packages in laboratory, greenhouse and field experiments. Lettuce is chosen as a model plant, as all cultivars grown in Israel and the Palestinian Authorities are susceptible to RKN, and accordingly suffer from yield loss. Compost of the black soldier fly larvae (BSFL, Hermetia illucens) is used as a rearing substrate for FLN and as organic fertilizer in the experiments. BSFL is a sustainable solution for animal and plant agriculture waste management, with potential as soil amendment in organic farming. The major research questions addressed are: 1) Which FLN and mites species do naturally co-occur in arable fields with known RKN history, thus having a good potential to interact as biocontrol agents? 2) Which FLN species best enhance predator fitness (e.g. reproduction, biomass) and do these FLN represent an alternative diet for mites in the presence of RKN? 3) What are the separate and synergistic effects of microorganisms associated with BSFL compost and their nematode grazers on predatory mite abundance, plant fitness, and on RKN biocontrol by mites? 4) What is the impact of BSFL amendment as arable practice on biocontrol function of mites as well as on soil health, plant resistance to foliar herbivory and plant yield? Overall, the intended trilateral collaboration will identify, evaluate and conserve indigenous FLN and soil predatory mites for the biological control of RKN. This will foster sustainable farming strategies to be adopted by the growers in Israel and the Palestinian Authority.