Shanks et al. used Arabidopsis mutants and transcriptomics to examine the role of cytokinin in infection by Heterodera schachtii. Both nematode infection and parasitism were impaired in Arabidopsis lines with reduced cytokinin sensitivity. These findings suggest that H. schachtii must strike a delicate balance between activating cytokinin signaling to a level sufficient to promote parasitism and avoiding a level high enough to trigger an immune response.