Manejo de plantas daninhas da cultura do arroz irrigado através de extratos alelopáticos e agentes biológicos

Abstract

The objective of this study was to evaluate the allelopathic potential of aqueous extract of leaves of different rice cultivars in germination and seed vigor of weeds Digitaria, Aeschynomene and red rice and search the mycoflora of S. montevidensis in order to identify species of pathogenic fungi with the potential to act as bioherbicide and verify their specificity as to plants of irrigated rice. The first experiment was conducted in a completely randomized design with four replications in a factorial design, where the first factor tested of fresh leaves of rice cultivars (BRS Querência, Irga 424, Roxinho and Cica 07) and factor B concentrations of the extract compared (0, 25, 50, 75 and 100%). Evaluations of germination, first count of germination, velocity of germination, shoot length and root, dry mass of shoot and root. In the second experiment, the experimental design was completely randomized with five replications and the treatments arranged in a factorial design where the first factor was composed of two species of fungi (Fusarium semitectum and Fusarium oxyosporum), previously isolated from lesions found in plants collected during phase of suvery in the region of Pelotas paddy and factor B compared six levels of Spore concentration (0, 1x103, 1x104, 1x105, 1x106, 1x107 spores ml-1) applied at the stadium where the plants had a leaf arrowhead and sagittate in rice plants at growth stage R4. Extracts from leaves of rice cultivars Cica 07, Querência, Roxinho and Irga 424, in high concentrations, reduce germination and seed vigor of Digitaria and Aeschynomene. The isolates of F. oxyosporum and F. semitectum are not effective in controlling S. montevidensis when applied in a unique way and the developmental stage of seedling leaf with a sagittate, however, when applied at flowering stage of rice plants, and cause losses in yield and reduction in root length.Keywords: Oryza sativa, Aeschynomene sp., Digitaria sp., Sagittaria montevidensis.