Controle da ferrugem do cafeeiro com óleos essenciais

Abstract

Coffee rust (Hemileia vastatrix) is the most important disease that occurs in practically all coffee producing regions of Brazil and world. The disease is difficult to manage and chemical control is still the main form of disease control, however, constant use of these products can result in selection of resistant pathogens. In this context, search for alternative methods to control coffee rust with less environmental impact is still one of greatest challenges for researchers. Thus the objective of present work was to evaluate efficiency of essential oils of Melaleuca alternifolia and Eremanthus erythropappus and Azadirachta indica in different doses to control coffee rust. In first stage, in vitro, effect of three essential oils on germination of H. vastatrix urediniospores was evaluated. The experiment was carried out in a completely randomized design with four replications and analysis of variance in a 3 x 5 +1 factorial scheme, with three treatments (essential oils of tea tree and candeia) and commercial oil based on Azadirachtin in five doses (0.0, 0.25, 0 , 50, 1.0 and 2.0%), and an additional fungicide treatment (Azoxystrobin + Cyproconazole). The three oils studied, inhibited germination of H. vastatrix urediniospores, in all doses tested, showing a percentage of germination similar to treatment with fungicide. For in vivo test, the lowest dose of three oils used in in vitro test (0.25%) was selected, applied to coffee seedlings cultivar Catuaí 144, alone and in mixture with the fungicide, at dose 0 , 5L / ha, and inoculated with H. vastatrix. The area under disease progress curve (AACPD) for incidence and severity, SPAD index (Soil Plant Analysis Development), plant height and dry weight of aerial part were quantified.The in vivo experiment was set up in random blocks with eight treatments (neem, tea tree, candeia, neem + Azoxystrobin + Cyproconazole, tea tree + Azoxystrobin + Cyproconazole, candeia + Azoxystrobin + Cyproconazole, Azoxystrobin + Cyproconazole and control-treatment witness) with four repetitions. The variables were analyzed statistically, applying the Scott-Knott test at 5% significance. The lowest incidence and severity were observed when using doses of oils mixed with fungicide. The lowest incidence occurred with application of E. erythropappus + Azoxystrobin + Cyproconazole with 92.3% efficiency and M. alternifolia + Azoxystrobin + Cyproconazole (90.7%) in relation to control. For severity, control was 94.98% when applied to A. indica + Azoxystrobin + Cyproconazole and 92.45% for M. alternifolia + Azoxystrobin + Cyproconazole. There was no significant difference for shoot dry weight, chlorophyll content and height. The oils studied have potential to control coffee rust. But studies are needed to better understand effects of its components on plant and how it affects pathogen. But studies are necessary to better understand the effects of its components on pathogens.