Toxicity of copper hydroxide, dithianon, fluazinam, tebuconazole and pyraclostrobin to Didymella applanata isolates from Serbia

Abstract

A study of the in vitro sensitivity of 10 isolates of Didymella applanata to copper hydroxide, dithianon, fluazinam, tebuconazole and pyraclostrobin, was conducted. The isolates were derived from diseased raspberry canes sampled during 2013 at five localities in western part of Serbia, known as the main raspberry growing region of the country. Prior to sensitivity testing experimental conditions for radial growth assay were optimized. The results showed that the temperature of 22°C, oatmeal agar medium and 12/12 hrs light/ darkness light regimen provided the best conditions for sensitivity tests. Most of D. applanata isolates were sensitive to the tested fungicides. The narrowest range of EC50 values was recorded for tebuconazole (1.42–2.66 mg L−1). The widest range of EC50 values was obtained for pyraclostrobin, ranging from 0.17 mg L−1 to 55.33 mg L−1. The EC50 values for the studied isolates were 39.48–51.19 mg L−1 for copper hydroxide, 12.12–18.73 mg L−1 for dithianon and 5.72–42.56 mg L−1 for fluazinam. According to resistance factor values, all D. applanata isolates were sensitive to copper hydroxide, dithianon and tebuconazole. Among tested isolates, six were highly resistant to pyraclostrobin (RFs in the range of 207.1–325.5) and two moderately resistant to fluazinam (RFs were 3 and 7.4), respectively.