Thrips associated with Judas trees (Cercis siliquastrum L.) and population fluctuation of Judas thrips, Thrips vulgatissimus Haliday in the Arghavan Strait of Ilam county

In this research, the fauna of thrips associated with Judas trees (Cercis siliquastrum L.), and the population fluctuation and spatial distribution of Judas thrips (Thrips vulgatissimus Haliday) were studied in the Arghavan Strait located in Ilam city (west of Iran) during the years 2022-2023. In each sampling, 20 trees and four branches of 20 cm on each tree in different geographical directions were selected as the sampling unit. Sampling was done every three days; the branches of Judas trees were shaken on a white plastic tray, and then the thrips were transferred into an Eppendorf tube containing 75% ethyl alcohol. A total of 10 thrips species were collected and identified. The results showed that the Judas thrips have two population peaks. The first population peak was observed on the first day of April 2023. The highest population density was obtained in the first peak with an average of 30.60 ± 6.23 thrips per sampling unit, and the highest density in the second peak with an average of 73.75 ± 7.64 thrips per sampling unit. The results of the spatial distribution based on Taylor’s power law methods showed that the spatial distribution was aggregated. In addition, geographical directions had no significant effect on the density of Judas thrips. Based on the goodness of fit, the Taylor’s power law method was more suitable than Iwao’s patchiness method for estimating the spatial distribution of this species.