Flutuação populacional e dependência espacial de Aleurocanthus woglumi Ashby, 1915 (Hemiptera: Aleyrodidae) em Citrus latifolia

Abstract

This study aimed to evaluate the populational fluctuation and to characterize spatial pattern of of citrus blackfly, Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) located at São José do Ribamar city, Maranhão state. The evaluations were carried out in a commercial Tahiti lime orchard (Citrus latifolia Tanaka) in a Yellow Red Argisol. The sex citrus blackfly adults were monitored using with 64 uniformly distributed 10x15 cm yellow sticky traps hanging down in branches at 1.5 m up to the ground were used to collect the insects from January 2007 to January 2008, which were replaced fortnightly (26 sampling dates). The samples of insects trap captured were counted at Entomology Laboratory (University of Maranhão) in São Luís. A global positioning system (GPS) and a geographic information system (GIS) were used to locate sample points, characterize distribution patterns, calculate aggregation area and map the distributions of the citrus blackfly adults within the lime orchard. Descriptive statistics was used for an exploratory analysis of data, while geostatistics parameters was used for evaluating spatial dependence of variable and generate contour maps by block ordinary kriging interpolation technique. A correlation analysis between citrus blackfly adults captured and environmental temperature were also executed. The results showed the non-existence of correlations between environmental factor temperature with insect populations in rainy and dry seasons but positive correlation between population level of males and total adults and entire period evaluation. The citrus blackfly adults were collected all year long. The insects showed a sazonal behavior with population density peaking at the rainy season. The periods of higher citrus blackfly populations are the March, May and July, where occurrence of males was greatest too. Lowest population was registered from November 2007 to January 2008. The spatial dependence was verified. The A. woglumi spatial distribution in the orchard is aggregated, adjusting to a spherical model in the rainy and dry seasons. The insects showed a mean aggregation area of 162,092 m2 at rainy season and 9,615 m2 at dry season. Therefore, in order to obtain a reliable estimate of citrus blackfly populations, at least one trap should be used per 17 hectares in rainy season and one trap per hectare in dry season.