Dinâmica populacional de afídeos (Hemiptera: Aphididae) em árvores cítricas no município de Nova Granada - SP / Population dynamics of aphids (Hemiptera: Aphididae) on citrus trees in Nova Granada County, São Paulo State, Brazil

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

Because aphids are possibly involved in the spread of viruses associated with a new and destructive disease, citrus sudden death (CSD), it is important to know their population dynamics in order to understand disease epidemiology. The goal of this research was to determine the main aphid species that colonize citrus groves [Citrus sinensis (L.) Osbeck] in CSD-affected areas of northern State of São Paulo, as well as to study their population dynamics. In order to establish procedures for sampling aphids that colonize citrus, a preliminary study of spatial distribution of these insects on the canopy of citrus trees was carried out in two sweet orange groves in Comendador Gomes-MG and Santa Cruz do Rio Pardo-SP. In each grove, 100 trees were randomly sampled in an experimental plot with 960 numbered plants. Each tree canopy was divided in three strata: i) lower (0 – 1,0 m); ii) medium (1,0 – 1,8 m); and iii) upper (>1,8 m). The canopy strata were subdivided in quadrants (E, W, N, S). Twelve young branches were sampled from each tree (1 per quadrant; 4 per stratum). By using analysis of variance, significant effects of plant and canopy stratum on aphid population were observed, with lower numbers of nymphs and adults found on the lower stratum than on the medium and upper strata. Aphid population was not influenced by quadrant or stratum x quadrant interaction. It was determined that sampling of 4 young branches (1 per quadrant) of the medium stratum from 150 citrus trees would be an adequate procedure for monitoring aphids on citrus trees, in order to obtain accurate population estimates for the population dynamics study. By using this sampling method, aphid surveys were carried out fortnightly in two sweet orange groves (‘Valência’ grafted on rangpur lime), 4 and 10 years old, in Nova Granada County, from April/2003 to April/2005. Simultaneous observations of mean number of young shoots/m2 of citrus canopy and mean shoot length were also conducted. By using multiple linear regression analysis, aphid numbers were correlated with local climatic variables (minimum, medium and maximum temperatures; relative humidity and rainfall) recorded 30 days before aphid sampling, as well as with phenological variables (mean number of young shoots/m2 and mean shoot length) recorded on the sampling date. Aphis gossypii Glover, A. spiraecola Patch, Toxoptera citricida Kirkaldy were the main aphid species sampled. A. gossypii and A. spiraecola were the prevalent species in the 4-year old grove, whereas T. citricida prevailed in the 10-year old grove. Aphid colonies were detected on citrus trees during periods of young shoot production, in different seasons, with either low (winter) or high (summer) rainfall. Mean number of young shoots/m2, mean shoot length and temperature were the main factors associated with aphid colony development on citrus trees. Peaks of A. gossypii, A. spiraecola and T. citricida alatae on citrus branches occurred during the winter months (July through September). A. spiraecola, A. gossypii and T. citricida differed in the ability to cause severe leaf deformation in the young shoots; this type of direct damage was mostly associated with colonies of the first species.

ASSUNTO(S)

amostragem distribuição espacial toxoptera citricida aphis sampling method morte súbita population dynamics pulgão citrus sinensis fruta cítrica climatic factors inseto-vetor dinâmica populacional

ACESSO AO ARTIGO

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