VARIATION AND CONSISTENCY IN SPATIAL-DISTRIBUTION AS MEASURED BY TAYLORS POWER-LAW

To investigate the spatial isotropy of Taylor's power law, data of the aerial population densities of western newer thrips, Frankliniella oc cidentalis (Pergande), were compared at 6 greenhouses in northeastern Ohio. The distributions were the same in all 6 houses despite differen ces in crop (host plant) and in thrips population growth and developme nt. Comparison with data from the literature on F. occidentalis distri butions obtained in houses with horticultural crops using closely simi lar sampling methods revealed a consistency of distribution over a ran ge of plant architectures. The consistency of power law results means that the same sampling program may be used for F occidentalis in a var iety of greenhouse crops. In contrast, samples taken within the canopy of a cucumber crop resulted in Taylor's power laws significantly diff erent fr om those obtained with samples taken above the canopy. Taylor 's power law appears to remain constant provided the same statistical population is being sampled. Sampling the same reproductive population under different conditions (e.g., stage, phenology, or habitat) can r esult in different power law estimates, as reported by some authors. P ossible reasons for power law differences and the significance of powe r law constancy also are discussed. Tables for optimum sample size are given for sampling F occidentalis in greenhouse crops using industry standard yellow sticky cards. In addition, it is shown how the number of samples required for a axed level of precision can be manipulated b y varying the sampling efficiency or size of sampler.