Seasonal activity and spatial distribution pattern of Eotetranychus frosti (Acari: Tetranychidae) in an unsprayed apple orchard of Kermanshah, Western Iran

Population density and spatial distribution pattern of eotetranychus frosti (mcgregor)was determined in an unsprayed apple orchard of kermanshah, western iran, from 31stmay till 7th november 2007. on each sample date 130 leaves were selected, with arelative variation of 4.31%. different methods of indices of dispersion, regressionmodels (taylor and iwao), morisita’s index and lloyd’s mean crowding to mean wasused to determine the spatial distribution pattern of this mite. the mean populationdensity of this mite per leaf was 2.079. the highest population density of e. frosti was in9th august (4.938 per leaf). index of dispersion (s2/m= 6.516), aggregation index (1/k=2.653) and lloyd’s mean crowding to mean (m*/m=3.653) showed an aggregateddistribution for this species. the taylor's power law and iwao's patchiness regressionmethods showed aggregated spatial distribution too. some changes in spatial distributionpattern from aggregated to random were observed using morisita’s index in differentsampling dates. three different coefficients of taylor, iwao and k were used to optimizethe sample size for future studies. the lowest optimized sample size (34.70) wasobtained by using the taylor's coefficients. spatial distribution parameters of e. frostican be used to improve a sampling program of this mite in a framework of an integratedpest management system.