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.
RESUMO O Brasil tem excelentes condições climáticas para a exploração comercial da goiabeira Psidium guajava L. (Myrtaceae); porém, em todo o país, a cultura é atacada por insetos-praga, sendo Triozoida limbata Enderlein, 1918
Introdução: Os drosofilídeos exóticos são encontrados principalmente em áreas abertas ou ambientes degradados e urbanizados, desde que nesses ambientes ocorram frutos carnosos, por serem considerados os seus principais locais de reprodução. Os frutos carnosos da lobeira, Solanum lycocarpum (Solanaceae), são exemplos de sítios de desenvolvimento das larvas de drosofilídeos, mesmo em estações com estresse hídrico. Objetivo: Conhecer a composição populacionais das espécies exóticas de drosofilídeos larvais hospedeiros de frutos de S. lycocarpum. Material e métodos: Os frutos de S. lycocarpum foram coletados semanalmente durante o período de amadurecimento e, posteriormente, pesados e armazenado individualmente em recipientes plásticos. Foram calculadas a proporção de frutos colonizados por drosofilídeos, a densidade de larvas e a viabilidade pupal. Resultados: Foram encontradas três espécies exóticas de drosofilídeos – Drosophila simulans (52,3%), Drosophila melanogaster (44,7%) e Drosophila repleta (3%). A proporção de frutos colonizados foi de 78,7%, com uma média de 8,8 ± 3,42 moscas por fruto. A taxa de infestação de pupário/kg de fruto foi de 186,9, com viabilidade pupal de 76,5%. Conclusão: Estas três espécies, por apresentarem hábitos alimentares generalistas, possivelmente estão reduzindo a abundância das espécies nativas por competição, podendo inclusive serem utilizados como bioindicadores de degradação ambiental.
The aim of this study was to carry out probabilistic analyses of the spatial distribution patterns of adults of Triozoida limbata Enderlein, 1918 (Hemiptera: Triozidae) in guava orchards. This study was conducted in four guava orchards in Ivinhema, Mato Grosso do Sul, Brazil. The samplings were conducted every fortnight from April 2012 to March 2014. A sampling area was set up for adult samples, and it consisted of 24 sampling units or plots with 15 plants in each (3 rows × 5 plants). A double-sided adhesive yellow trap was installed, 23 cm in length and 11 cm in width, around the central plant of each sampling unit, approximately 1.5 m from the ground. The dispersion rates (variance/mean ratio, Morisita index and Exponent k of the Negative Binomial Distribution) and the theoretical frequency distributions (Poisson and Negative Binomial) were calculated. Following the analyses, it can be concluded that the adults of T. limbata of the populations studied are randomly distributed in the four areas evaluated, with the sampling data fitting the Poisson distribution model.
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