Comparison of beat cloth and entomological net methods for determining faunistic indices of soybean in Rio Grande do Sul, Brazil

Lindolfo Storck,Claudia Carolina Cabral Antúnez,Jerson Vanderlei Carús Guedes,Jimmy Walter Rasche Alvarez,Alberto Cargnelutti Filho

doi:10.1590/0103-9016-2015-0164

Abstract

Estimates of diversity indices provide information on distribution, richness and abundance of species within a community. The aim of the current study was to estimate faunistic indices (richness, constancy, dominance and abundance) of the species collected by beat cloth and entomological net sampling methods in different soybean crops and to determine the sample size necessary to estimate faunistic indices. Fauna density from 100 soybeans crops located in nine municipalities in Rio Grande do Sul, Brazil, were evaluated. Thirty points, 20 meters apart from one another, were marked in the crops. At each point, insect pests and natural enemies were collected using the two sampling methods. Faunistic indices, including the average and interval estimates carried out by the resampling method, were calculated for each soybean crop. In the samplings using the beat cloth, richness > dominance = abundance > constancy, and using the entomological nets, richness > dominance > abundance > constancy. All faunistic indices other than dominance were greater when using the beat cloth method than those estimated by the entomological net method. The sample sizes required to estimate richness, constancy, dominance and abundance indices were 38, 78, 47 and more than 300, respectively, with an estimation error of 20 % of the average (p = 0.05). Higher values were observed when entomological net was used.

Highlights

Brazil is the world’s largest soybean producer (Glycine max (L.) Merrill) and outputting 82 million tons annually
The aim of the current study was to estimate faunistic indices of the species collected by beat cloth and entomological net sampling methods in different soybean crops and to determine the sample size necessary to estimate faunistic indices
Fauna in the soybean crop The total numbers of specimens collected in the 100 soybean crops in the three growing seasons were 18,717 and 9,423 insects using the beat cloth and entomological net methods, respectively

Summary

Introduction

Brazil is the world’s largest soybean producer (Glycine max (L.) Merrill) and outputting 82 million tons annually. Estimates of faunistic indices provide information on distribution, richness and abundance of species within a community. The advantage of such indices is that they generate analyzable data, and by definition, they are devoid of unity, allowing comparisons between communities sampled with a nonstandard method (Wade et al, 2006; Haddad et al, 2011; Martins et al, 2012). Studies on the diversity of beneficial and pest insects have been performed in different crops (Wade et al, 2006; Stürmer et al, 2012). Different sampling methods can be important to quantify the faunistic indices

Objectives

Methods

Results