ANáLISE DE CRESCIMENTO, INCIDêNCIA DE Rhizoctonia sp. E EFEITO ANTIXENOSE PARA A FORMIGA-CORTADEIRA Atta sexdens rubropilosa F. EM CLONES DE Eucalyptus grandis x Eucalyptus urophylla TRATADOS COM GIBERELINA1

摘要

The competitiveness of the forest sector in Brazil, as a result of climate conditions and technology used, makes the country occupy a prominent position on the world. Despite the high Brazilian growth in the forest sector, the development of research that provide increased productivity is necessary. This study aimed to evaluate the physiological effect of the application of gibberellic acid (GA3) in the accumulation of biomass of Eucalyptus grandis x Eucalyptus urophylla "E. urograndis GG 100" hybrid and also to verify the effect of this hormone application on the incidence of Rhyzoctonia sp. besides the antixenosis effect (not preferred) on the leaves by leaf-cutting ant Atta sexdens rubropilosa. The experiment was conducted in a bench, full sun, following a completely randomized design with five treatments and six replications. Cloned E. urograndis GG 100 seedlings, 120 days old, grown under full sun bench in 12 liter pots with a substrate based on subsoil, sand and manure were treated with 50 ml of GA3 according to following concentrations: 0, 50, 100, 150 and 200 mg L-1. Analyzes were performed 40 days after treatment imposition. The application of gibberellin intensified vegetative growth of Eucalyptus plants and promoted a greater accumulation of biomass than untreated plots in the same period of time. Seedlings treated with gibberellin showed vigorous vegetative growth, especially in the concentration of 150 mg L-1. In addition, the same plants exhibited higher preference to leaf-cutting ants and smaller leaf area damaged by fungus Rhizoctonia sp.