Sampling procedures for spittlebug adults in pastures of Brachiaria decumbens

Abstract

A sampling study of spittlebug adults in pastures of Brachiaria decumbens was conducted to find an appropriate number of sweep-net sweeps/sample. Considering the relative variation (SE/x) X 100, and the total number of sweeps in the sampling, 10 sweeps/sample were found to be better than 5, 20 or 40. The number of samples required for a particular level of relative variation at population densities > 16 spittlebug adults/10 sweeps remained the same, whereas at densities < 16, the number increased inversely. A regression model to convert relative estimates obtained by sweep-net method to the absolute estimate was presented. Considering the degree of precision and the time spent in sampling, the sweep-net method was superior to cage method. The distribution pattern of numbers of spittlebug adults in samples of 10 sweep-net sweeps, generally fitted the Poisson series. A sequential plan presented here would reduce the sampling time over the conventional (fixed sample numbers) sampling.