Analysis of spatial and temporal associations of adult and immature Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) in cucumber greenhouses

Abstract

In this study, we examined the spatial dynamics of the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae). Adult and immature F occidentalis were sampled weekly from two cucumber greenhouses on Jeju Island, Korea, from May to July in both 2003 and 2004. Spatio-temporal dynamics of immature and adult F occidentalis were analyzed and compared based on the Green's index, Taylor's power law (TPL) and spatial analysis of distance indices (SADIE). Based on the dispersion indices determined from the TPL and Green's, thrips were found to be aggregated in both greenhouses. The degree of aggregation differed significantly between adult and immature thrips according to the TPL. The SADIE index of aggregation and association probability were estimated and compared between stages and between sampling times. The aggregation values (I-a) for adults and immatures at most sampling points were indicative of a inconsistent pattern of aggregation. There were substantial spatial associations (10 out of 14 cases) between adults and immatures each week; however, the temporal stability of the spatial patterns of adults and immatures decreased over time. The spatial patterns of F occidentalis and their associations presented here provide the baseline information necessary to understand and predict plant damage and thrips dynamics in greenhouse environments.