Multivariate approach to quantitative analysis of Aphis gossypii Glover (Hemiptera: Aphididae) and their natural enemy populations at different cotton spacings

José B Malaquias,Carlos T Dos S Dias,Bruno P Brugger,Francisco S Ramalho,Aline Cristina S Lira,Carlos F Wilcken,Jéssica K S Pachú,José C Zanuncio

doi:10.1038/srep41740

Abstract

The relationship between pests and natural enemies using multivariate analysis on cotton in different spacing has not been documented yet. Using multivariate approaches is possible to optimize strategies to control Aphis gossypii at different crop spacings because the possibility of a better use of the aphid sampling strategies as well as the conservation and release of its natural enemies. The aims of the study were (i) to characterize the temporal abundance data of aphids and its natural enemies using principal components, (ii) to analyze the degree of correlation between the insects and between groups of variables (pests and natural enemies), (iii) to identify the main natural enemies responsible for regulating A. gossypii populations, and (iv) to investigate the similarities in arthropod occurrence patterns at different spacings of cotton crops over two seasons. High correlations in the occurrence of Scymnus rubicundus with aphids are shown through principal component analysis and through the important role the species plays in canonical correlation analysis. Clustering the presence of apterous aphids matches the pattern verified for Chrysoperla externa at the three different spacings between rows. Our results indicate that S. rubicundus is the main candidate to regulate the aphid populations in all spacings studied.

Highlights

Changing the conventional cotton agroecosystem structure is a common practice in Brazilian crops, and a reduced spacing between rows is one of the most commonly implemented changes
The variables that occurred at 35 days differed from those that occurred at 49, 56, 63, 98 and 112 days in 2013; there were differences in the occurrence of such variables at 35 days in comparison to the others in 2014, except for those that occurred at 42 and 112 days. These results showed that the fluctuation in the aphid population and that of its natural enemies is a function of the assessment time and depends on the cotton cultivation year, according to the multivariate perspective
Our results showed that fluctuations in the populations of aphids and natural enemies as a function of time depend on the cotton cultivation year; the effect of crop age does not depend on crop spacing

Summary

Introduction

Changing the conventional cotton agroecosystem structure is a common practice in Brazilian crops, and a reduced spacing between rows is one of the most commonly implemented changes. Multivariate analyses are valuable tools when in studies regarding the interactions among many species of organisms from different trophic levels They allow the exploration of structural links between a great number of variables and enable the assessment and prediction of effective biological control agents; they provide a means for habitat classification and the identification of features of the crops that are associated with the establishment, efficiency and population or community structure of natural enemies[9]. They may be used to select biocontrol agents that are able to colonize the crop of interest to the farmer[10]. The aims of the current study are: (i) to characterize the occurrence on the apterous and alate forms of A. gossypii and their natural enemies based on principal components, as well as (ii) to analyze the correlations among groups of aphids (apterous and alate) and natural enemies, (iii) to identify if the natural enemies responsible for regulating the A. gossypii population are different among the spacings studied, and (iv) to evaluate patterns of similarity in the occurrence of both aphids and their biocontrol agents at different spacings of the cotton crop in two different seasons (2013 and 2014)

Objectives

Results

Conclusion