Spatial Distribution Pattern of Tetranychus urticae Koch (Acari: Tetranychidae) on Different Rosa Cultivars in Greenhouse Tehran

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is an economically important pest of ornamental plant in Iran. The population abundance and spatial distribution were studied on five Rosa cultivars including Maroussia, Wendela, Elderado, Wenedetta, and Hot Lady during two growing seasons of 2011 and 2012 in greenhouse. The k parameter, index of dispersion, Lloyd’s mean crowding, Morisita’s index and regression methods (Taylor and Iwao) were used to estimate the spatial distribution pattern of mite. There was improved sampling program by k parameter and coefficients of regression models. The result indicated that the highest population density of T. urticae was early of July (2.47 per leaf) and early of September (4.11 per leaf). Also, a sequential sampling plan was developed using the fixed-precision method of Green for estimating the density of the mite. Populations on different Rosa cultivars, especially Maroussia, were aggregated during most of the growing season and negative binomial models fit data sets better than the Poisson series. The mean number of two-spotted spider mite per plant had significantly difference between all plant strata. The fitness percentage of cultivar Maroussia Rosa revealed a slight tendency towards the Poisson distribution, so that 58 and 14.1 percent of data sets from T. urticae on cultivar Wenedetta populations fit the Poisson distribution. These results fully support findings of distribution indices, indicating an aggregated distribution. Determining sampling program and spatial distribution pattern of the pest can effectively help to design and perform of IPM.