Avaliação da atividade fungicida de extratos e óleos essenciais sobre ferrugem asiática da soja

Abstract

Extracts and essential oils from plants have a great potential to control phytopathogens due to their direct fungitoxic action, inhibiting mycelial growth and spore germination, and their ability to induce the accumulation of phytoalexins in plants. The objective of this work was to evaluate the effect of different methanol extracts and essential oils on Asian soybean rust (Phakopsora pachyrhizi). The experiment was carried out in a green house and incubator. A completely randomized experimental design of seven treatments and ten replications was used. The soybean cultivar was BRS 245RR; the treatments consisted of essential oils and methanol extracts of the genus Schinus terebinthifolius (Brazilian pepper tree) and Trichilia silvatica (quebra-machado, catiguá-vermelho), the surfactant, Tween 80 (1% v/v), and water, as a control. The plants were sprayed with their respective treatments, and then artificially inoculated with the fungus about 24 hours later. The characteristics analysed were: number of leaflets per plot; chlorophyll index, plant height, intensity of the Asian soybean rust, number of leaflets with rust, number of leaflets with a burnt appearance. The plants sprayed with 5% (m/v) Schinus extract, and 1% (v/ v) Schinus oil showed greater intensity of the disease compared to those sprayed with water. These two treatments and 1% Trichilia oil caused an increased incidence of burned leaflets, indicating phytotoxicity to the crop.