Spatial Distribution of Nymphs of Triozoida limbata Enderlein, 1918 (Hemiptera: Triozidae) in Guava Orchards

Triozoida limbata is considered one of the leading pests of guava crop in Brazil. Its nymphs are responsible for sucking leaf borders, causing curling and drying of the leaves, and leaving them with a necrotic appearance. Knowledge of the spatial distribution of nymphs of T. limbata is essential for improving sampling and control techniques. The objective of this study was to perform probabilistic analyses of patterns of spatial distribution of nymphs of T. limbata in guava orchards. The study was conducted in four guava orchards in Ivinhema, Mato Grosso do Sul, Brazil. Samplings were performed every 15 days, from April 2012 to March 2014. To obtain the nymph counts, a sampling area was demarcated in each orchard, comprising 50 sampling units. In each unit, a sample was taken randomly from a shoot of 10 cm to 15 cm in length at the median height of the central plant. Dispersion rates were calculated (variance/mean ratio, Morisita index, and Exponent k of Negative Binomial Distribution) and the data obtained in the field were adjusted to the theoretical frequency distributions (Poisson and Negative Binomial). Following the analyses, we concluded that nymphs of T. limbata in the studied populations were randomly organized in the four areas that were evaluated, and the sampling data have been adjusted to the Poisson distribution model.