The highly-damaging root-knot nematode (Meloidogyne spp., RKN) cannot be reliably controlled using only a nematicide such as fosthiazate because of increasing pest resistance.  In laboratory and greenhouse trials, we showed that chloropicrin (CP) or dazomet (DZ) synergized the efficacy of fosthiazate against RKN.  The combination significantly extended the degradation half-life of fosthiazate by an average of about 1.25 times.  CP or DZ with fosthiazate reduced the time for fosthiazate to penetrate the RKN cuticle compared to fosthiazate alone.  CP or DZ combined with low or medium rate of fosthiazate increased the total cucumber yield, compared to the use of each product alone.  A low-dose fosthiazate with DZ improved total yield more than a low dose fosthiazate with CP.  Extending the half-life of fosthiazate and reducing the time for fosthiazate or fumigant to penetrate the RKN cuticle were the two features that gave the fumigant-fosthiazate combination its synergistic advantage over these products used singularly.  This synergy provides the opportunity for farmers to use a low dose of fosthiazate which lowers the risk of RKN resistance.  Farmers could combine DZ at 30 g m^–2 with fosthiazate at a low rate of 0.375 g m^–2 to control RKN and adequately control two major soil-borne diseases in cucumber greenhouses.