Distribuição Espacial e Amostragem Sequencial de Insetos de Importância Econômica para o Cultivo de Milho

Abstract

The fall armyworm Spodoptera frugiperda (J.E. Smith) is a serious pest in maize fields (Zea mays L.) in Brazil and all across the American continent. In this work, we analyzed the spatial distribution of corn plants infested with S. frugiperda, to be retrofitted to a sequential sampling plan based on the binomial count. Data were collected during the winter season between 2012 and 2013 in six maize fields located in the south of the Mato Grosso do Sul state. Each sampling area comprised 50 plots, each measuring 50 m2 (5 × 10 m) in area. The evaluations were performed on ten infested plants per plot week to total between five and seven samples per field. Through the indices of dispersion and frequency, we observed that the spatial distribution of the plants infested with the fall armyworm was aggregated, with a tendency towards randomness. The sequential sampling plan was developed in accordance with the Sequential Probability Ratio Test. The same error rates were used in this research (α and β = 0.05 %). The sampling plan resulted in two decision boundaries. The upper boundary S1 = 4.6257 + 1.438n (population control is recommended) and the lower boundary S0 = -4.6257 + 1.438n (population control was not necessary). Sampling size for the decision-making process to control S. frugiperda required thirteen sample units.