This research elucidates interactions between Globodera pallida and Rhizoctonia solani (AG3) by comparing disease development in potato plants inoculated with G. pallida and R. solani. The effects of juvenile population density and time of infestation on R. solani disease were investigated in controlled environments. Plants were inoculated with a range of densities of second-stage juveniles (J2) of G. pallida (800, 4000, 10 000, 20 000 and 40 000 J2/plant) and R. solani at 2, 4 and 6 weeks after planting and a single treatment of G. pallida density and R. solani alone. The experiment demonstrated that greatest disease incidence and severity occurred when high population densities of G. pallida were applied at an early stage of plant development. To determine if this effect could explain differences in R. solani disease incidence and severity following interactions with individual field populations of G. pallida, a glasshouse experiment was conducted using two populations of G. pallida with known hatching characteristics (fast and slow hatching). The experiment revealed that a combination of a fast-hatching population with R. solani caused significantly more R. solani disease incidence and severity than a population of G. pallida with slower hatching characteristics.