Phyllosticta leaf spot on ginger cultural characterization of the pathogen and effect of chemical treatments on disease control in Morretes, Paraná State, Brazil

Abstract

The objectives of this work were to determine the micelial growth curve of the pathogen and the sensitivity to some fungicides potencially eficient to disease control. The optimum temperature range for micelial growth of Phyllosticta sp. was between 25 and 27.5 °C. The maximum and minimum temperatures for micelial growth were 32.5 °C and 10 °C. Temperatures of 5 and 35 °C completely inhibited the growth of the isolates. Total inhibition of the micelial growth was observed with captan and mancozeb (1,000 mg a.i./ml) and triadimenol (100 mg a.i./ml). Partial reduction of the micelial growth was observed with iprodione, methyl tiofanate and chlorothalonil until 1,000 mg/ml. The chemical control of PLS was studied in a commercial area of ginger "Gigante", in Morretes, PR, where 18 sprays were carried out, with a break of 7 to 10 days, from December to April. The highest reduction of the area under the disease progress curve standardized (AUDPCs) was observed with the spray of chlorothalonil. With the application of dithianon, cupper oxychloride, folpet, mancozeb and captan it was observed AUDPCs between 15.05 and 18.61 lesions/leaf. Iprodione, benomyl, triadimenol and methyl tiofanate did not control the disease (AUDPCs between 20.03 and 25.04 lesions/leaf). The AUDPCs in the check plot was 35.88 lesions/leaf. There was no significant difference of vigor and of ginger yield between fungicide treatments. The cupper oxichloride was phytotoxic to ginger.