Interactions between belowground and aboveground heterotrophic communities that have no direct physical contact can be connected through the plant as the mediator of these interactions. The aim of this study was to explore two-way plant-mediated interactions between two herbivores; the root knot nematode (RKN) Meloidogyne incognita, and the two-spotted spider mite, Tetranychus urticae Koch (TSSM) on an optimal and a sub-optimal plant hosts for TSSM, Lima bean (LB) (Phaseolus lunatus), and tomato (Solanum lycopersicum) respectively. To test RKN preference, we used two-way glass olfactometers to determine the response of RKN to Lima Bean plants that were exposed to TSSM versus a non-exposed LB plant. RKN consistently infected the non-exposed plants at a significantly greater rate than the TSSM exposed plants. For the aboveground experiments, we used leaf discs and two-way olfactometers choice tests of TSSM to RKN infected plant against a non-exposed plant, at different days post-inoculation (DPI) with RKN. Significantly more TSSM were found on LB plants that were infected with RKN compared to non-infected plants only at 25 DPI. On tomato plants, TSSM significantly preferred RKN infected plants at 1 DPI. We also tested the effect of the inoculation (1 DPI) entomopathogenic nematodes (EPNs), Steinernema carpocapsae on tomato plants, and found that TSSM preferred the EPN inoculated plants compared to non-inoculated tomato. We carried out a non-choice performance test for TSSM in both LB and tomato plants, on plants inoculated with RKN versus clean plants, and observed no effect of RKN exposure on TSSM performance
