[Seasonal variation of immature stages of Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) in Citrus sinensis orchards under two management systems].

Phyllocnistis citrella Stainton is considered an important pest of citrus, causing both direct (reduction on the photosynthetic area) and indirect damage (facilitation of invasion by bacteria that cause citrus canker). The lack of information about the population dynamics of P. citrella, considering the cultivation systems and varieties grown in citrus orchards in Rio Grande do Sul, Brazil, motivated this study. It aimed to evaluate the seasonal variation of immature stages of P. citrella, from June 2002 to July 2003, in two orchards of Citrus sinensis, cv. 'Valencia', one maintained according to organic management principles and the other under conventional ones. Fortnightly samplings were carried out, being one shoot collected from each one of 27 randomly chosen plants. The leaves were analyzed for the presence of eggs, larvae, pupae and mines of P. citrella. Leafminer was recorded from October 2002 to April 2003 in the organic orchard, and from November 2002 to July 2003 in the conventional one. A relationship between population size and resource availability (young leaves) was observed. However, population establishment does not depend exclusively on the existence of resources, but also on suitable climatic conditions. This was evidenced by the absence of attacks on the first shooting, which began in late winter. Meteorological factors and resource availability as a whole explain about 64% and 53% of the observed variation in the population size of P. citrella, respectively in the organic and conventional orchards.