Spatial distribution of Brevicoryne brassicae and Diaeretiella rapae and development a fixed precision sampling plan

Knowledge of spatial distribution pattern provides useful information about the main behavior of a species. From research point of view, dispersion pattern data could be useful for determining sampling pattern, optimal sample size and organizing sequential sampling plan. Sampling of pest and natural enemies populations is a key component in each integrated pest management program. From April to June 2010, cabbage aphid, Brevicoryne brassicae (L.) and its parasitoid Diaeretiella rapae Mc\'Intosh populations were sampled in two canola fields irrigated with two different methods (flooding and sprinkler irrigations) weekly. Taylor\'s power law and Iwao\'s patchiness regression methods were applied for determining spatial distribution pattern. Using Taylor\'s power law the b coefficient for cabbage aphid population in sprinkler and flood-irrigated canola were 1.77± 0.211 and 1.759± 0.122 and for D. rapae were 1.493± 0.0667 and 1.527± 0.125 respectively. These parameters showed the clumped dispersion pattern for both species at both irrigation systems. Scince Taylor\'s power law described variance - mean relationship better, estimated α and β were used for developing a fixed-precision sampling plan for cabbage aphid. The obtained results could be useful for management of B. brassicae in canola fields.