Dinâmica populacional da mosca-negra-dos-citros Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) em Citrus spp. no município de São Luís - MA

Abstract

The citrus blackfly is a fitofague pest which places itself in the abaxial face of leaves and has been turning into a serious threat to Brazilian fruit farming. This paper aims at knowing the populational floating of A. woglumi within an one-year period, to determine the time with the highest occurrence of this insect and its populational peaks, as well as verifying the distribution of this pest in Citrus spp. plants in the Brazilian town of São Luís, Maranhão. To study the blackfly population dynamics, 10 (ten) plants were chosen at random in each orchard, and 20 (twenty) leaves were collected in each plant, from July 2006 through June 2007, in order to count the number of postures, eggs and nymphas. To determine the vertical spreading of A. woglumi, the plants were divided into quadrants: North, East, South and West, from which 5 (five) leaves/quadrant were taken, totalling 200 (two hundred) leaves in each area. Regarding vertical spreading on the plant, the statistic delineation was determined by combining two periods of time (dry and rainy), with 4 quadrants, obtaining a 2x4 factorial with 13 repetitions (collections) and the averages were submitted to Tukey test, at a 5% probability. In the UEMA and Itapera locations, there was a reduction in the populational density in all the phases studied during the periods with highest pluviometric precipitations (January through June 2007). Regarding the distribution of A. woglumi in Citrus spp. plants, one could observe that in both locations the insect spread uniformly in the tree top, i.e., there wasn’t any difference in the dispersion of the number of postures, eggs and nymphas among the tree quadrants and the highest populational levels of A. woglumi occurred in the low precipitation period (July through December 2006).