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. thepopulation abundance and spatial distribution were studied on five rosa cultivarsincluding maroussia, wendela, elderado, wenedetta, and hot lady during twogrowing 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 ofmite. there was improved sampling program by k parameter and coefficientsof regression models. the result indicated that the highest population densityof t. urticae was early of july (2.47 per leaf) and early of september (4.11 perleaf). also, a sequential sampling plan was developed using the fixed-precisionmethod of green for estimating the density of the mite. populations on differentrosa cultivars, especially maroussia, were aggregated during most of thegrowing season and negative binomial models fit data sets better than thepoisson series. the mean number of two-spotted spider mite per plant had significantlydifference between all plant strata. the fitness percentage of cultivarmaroussia rosa revealed a slight tendency towards the poisson distribution, sothat 58 and 14.1 percent of data sets from t. urticae on cultivar wenedettapopulations fit the poisson distribution. these results fully support findings ofdistribution indices, indicating an aggregated distribution. determining samplingprogram and spatial distribution pattern of the pest can effectively help to designand perform of ipm.