population density and spatial distribution pattern of empoasca decipiens (hemiptera: cicadellidae) on different bean species

the population density and spatial distribution pattern of empoasca decipiens paoli were etermined in tehran area, iran, during 2004-2005 on four species of common bean phaseolus vulgaris (l.) var. talash, lima bean p. lunatus (l.) savi ex hassk. var. sadaf, rice bean p. calcaratus roxb. var. goli and cowpea vigna sinensis (l.) var. parastoo. the higher and lower mean population densities of e. decipiens per leaf were observed on parastoo cowpea (18.85 in 2004 and 29.94 in 2005) and talash common bean (1.08 in 2004 and 0.37 in 2005), respectively. spatial distribution pattern of e. decipiens was described on these four bean species using variance to mean ratios, taylor's power aw coefficients and iwao's patchiness regression methods. the spatial distribution pattern of this pest in most cases as aggregated and in a few cases random. in 2004, collected data were in a better fitting with aylor's model in comparison with iwao's model on talash common beans (r2= 0.879) as well as on goli rice bean (r2= 0.967). iwao's model explained the distribution data of 2004 and 2005 on sadaf lima beans (r2= 0.746 and 0.906, respectively) more appropriately than taylor's model (r2= 0.541 and 0.828, espectively). it is concluded that bean species influence the population density and spatial istribution pattern of e. decipiens. spatial distribution parameters can be employed to develop a sampling program and to estimate the population density of this pest.