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

Abstract

Objective: To compare the efficiency of a 30x30x5 cm iron sampling frame (Frame30) with a smaller 15x15x5 cm one (Frame15), as sampling method for spittlebug eggs [(Aenolamia albofasciata (Lallemand)] that reduces the amount of soil removed, optimizes time used, 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, from which 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 between plots (P<0.0001), but not in the plot-sampling frame interaction (P=0.1509). The optimal sample size (accuracy 0.1) was smaller with Frame15 (40, 27, 57 and 25), compared to Frame30 (65, 34, 61 and 34). Both frames estimated a conglomerated spatial arrangement of eggs using three methods. Limitations on study/implications: This study suggests changing the sampling frame used in Veracruz, Mexico, for a smaller, more efficient one. Findings/conclusions: Frame15 reduced by 75% the soil removed, provided more accurate population estimates, and simplified field and laboratory management, compared with Frame30.