Ferrugem do pessegueiro e seu efeito na desfolha e na concentraç ão de carboidratos em ramos e gemas

Abstract

This work aimed to evaluate the relationships between rust intensity (incidence and severity), disease induced defoliation and total carbohydrate level in buds and brushes of "Chimarrita" peach trees in a Brazilian subtropical region (Curitiba, Paraná). Rust intensity range was generated by four fungicide-spraying treatments (non-spraying; regular fungicide spraying from December to January; December to February and December to April) and the experiments were carried out over two years and six replications per treatment. Defoliation, incidence and severity were assessed over time in two previously marked one-year-old mixed branches, each one on opposite sides of each tree. Carbohydrates were analyzed twice each year (March and May) by sulphuric phenol method (absorbance at 490 nm). AACPD in 2005 was nearly twice as high as that of 2004 for the control, and all other treatments differed from the control. A positive correlation was observed between severity and defoliation, indicating effective pathogen interference in peach trees' defoliation process in the subtropical region. Total soluble carbohydrate levels in branches with no buds of the December-April spraying treatment were higher than the nonspraying treatment levels, showing the importance of post-harvest defoliation. Copyright by the Brazilian Phytopathological Society.