Sequential sampling plans with fixed precision levels for spotted alfalfa aphid, Therioaphis trifolii Monell (Homoptera: Aphididae) in alfalfa (Medicago sativa L.)

The objective of this paper was to design sequential sampling plans for the spotted alfalfa aphid (Therioaphis trifolii Monell) with fixed precision level, for density estimation and decision making. The study of spatial pattern based on Taylor's Power Law and Iwao's regression, showed different degrees of clumping of T. trifolii populations in alfalfa crops, depending on the developmental stage of aphids. The sequential sampling plan for decision making was calculated using two economic thresholds based on the height of the crop. The sequential sampling models developed by Kuno and by Green, were used to calculate stop lines. Green's model is recommended because Taylor's Power Law's regression yielded higher determination coefficients than Iwao's method.

Insecta; spatial pattern; Integrated Pest Management