Controle alternativo da queima das folhas do inhame (Curvularia eragrostidis) (Henn.) Meyer

Abstract

The taro leaf blight (Curvularia eragrostidis) occurs regularly in producing areas, causing significant losses in crop yield. This fungus can present Morphophysiological variability. Attempts to control the disease have been inefficient and lack of registered pesticides for culture has led to the search for natural alternatives. The objetive of this study was to characterize C. eragrostidis morfofisiologicamente and evaluate the effect of natural products on disease control. The means of PDA, LCA, CA, ADA and IDF culture were used to evaluate the mycelial growth of the fungus. In the media PDA, CA and LCA cultural characterization was performed. Under conditions of continuous darkness, continuous light and alternating light (12 hours), in the means PDA, CA LCA and sporulation of the fungus was evaluated. The mycelial mass determination was performed by growing the fungus in liquid culture media PD, C and LC and drying at 60 ° C for 48 hours. In the evaluation of natural products mycelia discs were transferred to Petri dishes containing PDA médium Products: cassava (40%); garlic extract (20%); melon extract Sao Caetano (20%); peppermint oil (100mL); Ecolife ® (20%); Trichoderma sp. (108 conidia mL-1); fungicide mancozeb (2.0 gL-1). The evaluation of percent mycelial inhibition was carried out after seven days of incubation. "In vitro" products tested were applied on the leaves of cv. Costa (Dioscorea cayennensis). Two days later, the plants were inoculated with a pathogen suspension (1.7 x 106 con.mL-1). The results showed that the growth of the fungus was not affected by culture media. The cultural characteristics of the isolate of C. eragrostidis varied according to the substrate used, but in general the colonies sporulation distributed around the perimeter of the central plate, mycelium greenish gray moss green color with smooth surface contour and white borders with frayed appearance. The highest rates of sporulation of C. eragrostidis occurred in the middle of PDA in alternating light and continuous dark regimes, with averages of 2.84 x 106 con.mL-1 and 2.42 x 106 con.mL-1, respectively. The greatest amount of mycelial mass was provided through LC. All the products tested were capable of inhibiting the mycelial growth of the fungus, and the Ecolife ® and cassava promoted inhibition of 100%. The extracts of garlic and melon Sao caetano, oil of peppermint, Trichoderma sp. And mancozeb were able to reduce the severity of leaf blight yam.