The average (+ s.e.m.) numbers of predatory mites (A. swirskii) on plants 28 days after they were released.

(a) Distance between neighbouring plants 0.6 m. Predators were released on the plant at 0 m, on which whiteflies were also released. The average number of predators differed among plants (GLM, F_4,10 = 14.7, P<0.001). (b) Distance between neighbouring plants 2 m. Predators were either released on the plant on which whiteflies were released at 0 m (Predators at 0 m), on the plant at 2 m (Predators at 2 m) or both on the plant at 0 and 2 m (Predators at 0 and 2 m). The average number of predators differed among plants in all three treatments (Predators at 0 m: F_4,15 = 44.0, P<0.001; Predators at 2 m: F_4,15 = 17.3, P<0.001; Predators at 0 and 2 m: F_4,15 = 12.4, P<0.001). Within each treatment, bars with different letters differ significantly (contrasts after model simplification). See Table 1 for a summary of the release schedule.