In vitro sensitivity of tomato early blight disease agent, Alternaria alternata to some fungicides on tomato

Early leaf blight is a common fungal disease caused by Alternaria alternata (Fr.) Keissler). Various fungicides are used for the chemical control of the disease. As a result of frequent use of fungicides, decreased susceptibility of the pathogen may be observed. In this study, susceptibility levels of early leaf blight (A. alternata), which is a problem in tomato cultivation areas, were determined against azoxystrobin, tebuconazole and mancozeb. Sixty A. alternata isolates were obtained from 121 infected plant samples collected from the Antalya, Ankara, Bartın, and Zonguldak provinces in 2013 and 2014. Pathogenicity tests revealed that the disease severity of the isolates varied between 50-85% on average. The susceptibility of the isolates to azoxystrobin, tebuconazole, and mancozeb was determined by radial growth tests and ED50 values against azoxystrobin, tebuconazole and mancozeb were determined as 0.4 ppm, 0.6 ppm and 0.6 ppm, respectively. Polatlı isolate was the most susceptible isolate against three active substances. Alanya isolate with ED50 value of 452 ppm. against azoxystrobin, a Derbent isolate with an ED50 value of 14.45 ppm. against mancozebe, Serik, and Kayaburnu isolates, with ED50 values of 33.61 ppm. against tebuconazole showed the highest resistance. In this study, it was determined that some isolates developed resistance to these fungicides.