Sampling efficiency of different sample units and procedures to sample spittlebug eggs

Abstract

A sampling study of spittlebug eggs in pastures of Brachiaria decumbens Stapf was conducted by using samples of 25, 50 and 75 cm² of the pasture. The sampling efficiency of three sample units was compared by calculating the number of samples necessary to obtain a certain level of precision (proportion of standard error to mean expressed as a percentage). The sampling efficiency of 50 cm² sample unit was poor in comparison to 25 and 75 cm² . To obtain the same level of precision, e.g., 20%, the total pasture area to be examined was slightly smaller for 75 cm² unit than for 25 cm² at lower egg density (1/25 cm²);however, such advantage of the 75 cm² disappeared at egg density of 4/25 cm² . Based on this finding and the fact that fewer samples would be taken in the case of 75 cm² than the 25 cm² unit, the use of former was suggested. The distribution pattern of number of eggs per 25 or 50 cm² of pasture fitted the negative binomial series.