Sampling unit and optimal sample size for the detection of Aeneolamia albofasciata (Lallemand) eggs in sugarcane

Abstract

ABSTRACT

Objective: To compare the efficiency of a 30x30x5 cm iron sampling frame (Frame30) with a smaller 15x15x5 cm one (Frame15), as a sampling method that reduces the amount of soil removed, optimizes employed time, and reduces the sampling effort.

Design/methodology/approach: Mean, variance, coefficient of variation, sampling effort, spatial arrangement, and sample size were determined with both sampling frames. Forty systematic soil samples were obtained using each frame in two plots planted with the variety MEX 69-290 and two others with MEX 91-662. Each soil sample was mixed and homogenized, to obtain a subsample of 250 g, where eggs were extracted by decantation in saline solution.

Results: Both frames estimated different numbers of eggs in the four plots ( ) (Frame15: 2.71±1.71; 3.49±1.81; 2.74±2.08; 4.44±2.22; Frame30: 4.42±3.58; 6.65±3.92; 4.40±3.45; 7.84±4.54). Significant differences were found between sampling frames (P<0.0001) and plots (P<0.0001), but no differences (P=0.1509) in the plot-sampling frame interaction. The optimal sample size (precision 0.1) was smaller with Frame15 (40, 27, 57 y 25), compared to Frame30 (65, 34, 61 y 34). Both frames estimated a conglomerated spatial arrangement of eggs using three methods.

Limitations on study/implications: This is a proposal to change the sampling frame used in Veracruz, Mexico for a smaller, more efficient one.

Findings/conclusions: Frame15 reduced by 75% the soil removed, provided more precise population estimates, and simplified field and laboratory management, compared with Frame30.

Keywords: spotted spittlebug, eggs, sampling metal frame, systematic sampling.