COMPARISON OF SAMPLING METHODS AND DEVELOPMENT OF A SEQUENTIAL SAMPLING FOR CHRYSOMELIDS AND LEAF-KEEPERS IN BEANS

Abstract

Direct observation, cloth, D-Vac and  Sweepnet methods of capture were compared against an absolute method of sampling, in order to find out their effi­ciency in estimating populations of Dia­brotica balteata LeConte, Cerotoma fa­cialis Erickson (Coleoptera: Chrysomeli­dae) and the leafhopper Empoasca kraemeri Ross and Moore (Homoptera: Cicadellidae) on beans. The spatial distribution of these insects, in which economic damage levels have al­ready been established, was studied with the best sampling methods. A sequential sampling model was also developed. Direct observation and D-Vac were efficient for all of the insects. The cloth method was efficient for D. balteata and chrysomelid complex. The sweep net was efficient for estimating E. kraemeri adults, and the only method available for estimating E. kraemeri nymphs was the direct observation. Though there were differences between crops, the !spatial distribution was ge­nerally contagious for chrysomelids and nymphs of the leafhoppers. For these species, the models which fit the best were the binomial negative and the Ney­man type A. The regression calculation between aggregation means and popula­tion means, permitted to calculate the ne­cessary decision lines for developing a sequential plan for leafhopper and chrysomelids on beans.