Padrões populacionais de Triozoida limbata (Enderlein,1918) (Hemiptera: triozidae) em diferentes cultivares de goiabeira, Psidium guajava (Myrtales:myrtaceae)

Abstract

The global fruit production is characterized by the cultivation of a wide diversity of species and varieties of fruit plants, among them the crop of guava, Psiduim guajava L, (Myrtaceae) has highlighted both socially and economically. The culture of guava showed an increase in plantation areas in Brazil, where largest portion of the fruit is destined for industrialization. However, there is a significant growth of the fruit market in natura. Triozoida limbata (Enderlein) (Hemiptera: Triozidae) is a key pest of guava in Brazil. Their nymphs suck the edges of new leaves, causing winding, drying, leaf necrosis, reduce photosynthesis, and as a result, causes severe losses to production. The use of insecticides and fungicides has been held frequently during the year in an attempt to protect new shoots against T. limbata’s attack. Chemical compounds of plants are involved in several metabolic and behavioral processes of the phytophagous species of insects. The development of research is essential to investigate the plant diversity, combined with other methods that are used for the purpose of insect management in sustainable production systems. Knowledge of the spatial distribution of insect species with agricultural importance is of fundamental importance for Integrated Pest Management (IPM). This studies, beyond to their ethological importance, are usefull to help in IPM of arthropods of agricultural importance. Thus, this study aimed to seek knowledge to minimize the costs of production in IPM, assessing nonpreference of T. limbata by guava cultivars in the field, determine the location of longitudinal and transverse distribution of this pest species, determine the spatial distribution pattern of infestation of nymphs and adults of T. limbata in a guava orchard with different cultivars. The evaluations were conducted in the didactic orchard located at EMBRAPA Produtos e Mercado in Dourados-MS, from May 2013 to July 2014. This orchard contains eight cultivars: ‘Pedro Sato’, ‘Kumagai’, ‘Paluma’, ‘Cascuda’, ‘Século XXI’, ‘Sassaoka’, ‘Novo Milênio’ and ‘Tailandesa’. The row spacing is 7 m x 5 m. The plants were evaluated every two weeks, noting the number of nymphs and adults of triozids present in the guava trees: from the apex to the second pair of fully expanded leaves (three sheets at random). We evaluated four main branches by plant located in the upper third of the canopies. Moreover, each plant was monitored with a yellow sticky traps (10 x 15 cm) attached at the height of the canopy to capture adults, and was replaced every 15 days. The design was completely randomized blocks, with eight treatments (eight cultivars) and four replications (three plants per repetition). We used the non-parametric Kruskal-Wallis statistical tests to determine the analysis of variance, two-sided Bonferroni-Dunn’s test, to make pairwise comparisons. The branches of the cultivars ‘Cascuda’ and ‘Kumagai’ were the least preferred by nymphs T. limbata; the least preferred by adults is the cultivar ‘Sassaoka’. In the traps, fewest adults of T. limbata were obtained 12 in the cultivars: ‘Cascuda’, ‘Kumagai’ and ‘Sassaoka’. It was found that there was no difference in the distribution of nymphs and adults of T. limbata between the positions of branches in the stands (between guava trees, nor between lines of guava trees). Through the dispersion indexes (index variance/mean; Morisita and K negative binomial) and theoretical frequency distributions (Poisson, negative Binomial and Binomial positive), it was found that under these conditions, the spatial distribution of nymphs and adults T. limbata is aggregated, adjusting the negative binomial.