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

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.

Attractive food in the sampling and seasonality of insects in soybean-oats succession

“…Sampling defines the population of insects present in a particular area of cultivation, being a presupposition for decision making under the precepts of Integrated Pest Management (Guedes et al, 2006;Riffel et al, 2012). Different techniques to know the population of a certain species of insect-plague or natural enemy are spent by technical assistants and producers, the most known and used are: direct observation, pinworm, entomological net, light trap and sexual pheromone trap (Silva et al, 2014;Pasini et al, 2015;Storck et al, 2016;Garlet et al, 2016).…”

“…The efficiency of the different sampling techniques is still widely discussed and is directly related to the number of replicates (sampled area), morphological aspects of the host plant, climatic variables and the intrinsic characteristics of the species to be sampled (Storck et al, 2016;Engel et al, 2017;Pasini et al, 2018). In this way, new tools for insect sampling are being launched every year, and the entomofaunistic studies are still necessary to know their real efficiency and environmental impact.…”