Distribuição espaço-temporal e flutuação populacional de lagartas desfolhadoras da soja

Abstract

This work aimed to analyze the spatial-temporal distribution and population fluctuation of soybean defoliating caterpillars, during the development cycle of the crop. Thus, this will be presented in two chapters. Chapter one, presents a geostatistical characterization of the caterpillars spatial distribution in soybeans and chapter two describes the main species of soybean caterpillars and their behavior during the crop cycle. Study was carried out in the experimental area of the Universidade Federal de Santa Maria, Santa Maria, Brasil, at 2008/09 and 2009/10 growing seasons. In the area of 6,6 ha of soybean a grid sampling of 25x25m was established. A total of 105 points were marked on the field with GPS navigation. The samplings were performed in two ways: 1) from pre-emergence until V3, direct counting; 2) from V4 until harvest, with beating cloth, performing two evaluations per point. Caterpillars were placed into plastic cups and sent to the Entomology Laboratory of UFSM for species identification and quantification. To study the populational distribution was considered the total populational density and species of each sample point was obtained by analysis of spatial variability using semivariograms. Maps were generated with the software ArcGIS 9.3 and spatial dependence estimated by classification of Cambardella et al. (1994). To study the population dynamics of soybean caterpillars species, results were submetted to statistical analysis, using Microsoft Excel software. Pearson correlation was with 5% mistake probability was used for establishing correlations between the number of caterpillars species and meteorological variables, precipitation and temperature. Adjusted models are different for every species and phenological stage of culture, the grid of sample used is appropriate to characterize accurately the spatial distribution of soybean larvae. The main species of soybean caterpillars in Santa Maria are Anticarsia gemmatalis, Pseudoplusia includens and Spodoptera eridania; the occurrence of defoliating caterpillars is higher in the reproductive phase of soybean.