Exogenous RNA interference exposes contrasting roles for sugar exudation in host-finding by plant pathogens

•Sugar transporter genes 1 and 2 (STP1, STP2) were silenced in tomato seedlings using exogenously applied dsRNA.•Silencing STP1 and STP2 reduced glucose and fructose concentrations in root exudates, but had no impact on xylose.•Meloidogyne incognita is attracted to and activated by the monosaccharide sugars glucose and fructose.•Globodera pallida a specific pathogen of Solanaceae plants is not attracted to, or activated by the monosaccharides.•Tomato root exudate from STP1- and STP2-silenced seedlings failed to attract/activate M. incognita as strongly as controls.