Essential oils for control of âColletotrichum truncatumâ and Asian soybean rust. / ÃLEOS ESSENCIAIS PARA O CONTROLE DE âColletotrichum truncatumâ E FERRUGEM ASIÃTICA EM SOJA

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

The objective of the work was to evaluate the antifungal activity of essential oils via treatment of soy seeds in the control of the fungus Colletotrichum truncatum and on the Asian soy rust. For that, the essential oils of Hyptis marrubioides, Aloysia gratissima and Cordia verbenacea were tested. In the first experiment, the oils were initially tested in vitro on the fungus C. truncatum, evaluating the germination, micelial growth, conidium production and the produced conidium viability. Soon after, the soy seeds were inoculated and treated with the oils and with fungicide. The incidence of the fungus was evaluated in the seeds and at their germination. The seeds were planted in trays in which, the stand, germination, percentage of dead seedlings, Emergence Speed Index (ESI), plant height and biomass dry of the aerial part were evaluated. The experiment was set up in random blocks (RBD) with 4 repetitions of 50 seeds each. The tested essential oils affected the germination, the growth and the reproduction of the fungus, but it did not affect the viability of the produced conidia and the seed germination, even at high concentrations. It was also verified that, the higher the concentration of the oils, more effective was the treatment of the seeds and that, even at the concentration of 1% of all of the essential oils, a promising result was obtained in relation to the commercial fungicide recommended in the treatment of soy seeds for the control of the C. truncatum fungus. In preventive treatment in the control of the Asian soy rust, in vitro tests were done using the oils at the concentrations 0.05; 0.08; 0.1; 0.3; 0.5 and 1%, the pyraclostrobin+ epoxiconazole based fungicide mixed in the Agar-Water culture plus the control. The in vivo test was conducted in a greenhouse, using the MGBR-46 (Conquista) cultivar. The treatments consisted of the three oils at concentrations of 0.05; 0.1 and 0.3%, the fungicide plus the control, applied at four pulverization times of 0, 6, 12 and 24:00 before the inoculation of the pathogen. The assay was set up in RBD with 5 repetitions. The evaluations of the disease severity were made every 7 days. All of the oils at all of the concentrations completely inhibited the germination of the Phakopsora pachyrhizi urediniospores. In the in vivo test , it was observed that there was no difference among the tested oils; all presented soy rust control, even at the lowest concentrations. The time of pulverization up to 24 h before the inoculation, for most of the treatments, did not influence in the severity of the disease. There was however, an increase of the severity with the increase of the time between the inoculation and the treatment. All of the treatments, at all of the inoculation times reduced the progress of the severity, many presented a reduction equal to the pyraclostrobin+epoyconazole based fungicide recommended for rust control.

ASSUNTO(S)

tratamento de sementes treatment of seeds alternative control. Ãleos essenciais controle alternativo. fitopatologia essential oils

ACESSO AO ARTIGO

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