Spatial distribution of Spodoptera frugiperda in the wasteland of southern Pernambuco state, Brazil

Abstract

The fall armyworm ( Spodoptera frugiperda) causes damage and reduction in maize production and is considered a pest difficult to control, thus determining its spatial distribution pattern contributes to the development of suitable sampling and control strategies. The aim of this study was to evaluate the spatial distribution of Spodoptera frugiperda in maize culture under the conditions of the wasteland of southern Pernambuco state. The experiment was conducted at the Experimental Station of Brejao - ‘Instituto Agronomico do Pernambuco’ (IPA) from April to May 2012. The study area consisted of 100 plots of 60 m2, where 10 plants per plot were weekly sampled at random. In each plant, the number of small and large larvae of S. frugiperda was counted on the leaves and the husk of ears. According to the data observed, the aggregation indices (variance/mean ratio, Morisita’s index, Green’s Index, and Exponential k of a negative binomial distribution) indicated aggregate distribution for both small and large caterpillars, and the negative binomial distribution was the most appropriate model to represent the distribution pattern of small larvae of this pest in the field. In maize crop in the wasteland of southern Pernambuco state, S. frugiperda presents aggregate pattern of distribution and tends to spread from the points of aggregation and colonize form the border into the center of cultures.