First detection of Cryptosporiopsis tarraconensis on hazelnut in Türkiye and control potency of some antifungal agents

Hazelnut (Corylus avellana L.) is one of the most important agricultural products of Türkiye with over 77% of total global production occurring here. Some diseases such as powdery mildew, nectria canker and bacterial blight negatively affect hazelnut production. Changing climatic conditions have enhanced the emergence of new diseases in hazelnut orchards. This study was carried out to determine the causative pathogen of some disease symptoms seen in hazelnut orchards in 2021 and to investigate possible control methods. The isolated pathogen – Cryptosporiopsis tarraconensis – was identified by morphological and molecular methods. The effects of different doses of some fungicides on mycelial growth of C. tarraconensis were tested in plates in in vitro experiments as well as on detached leaves. According to the result, the EC₅₀ values of fluxapyroxad + difenoconazole, boscalid + pyraclostrobin and pyrimethanyl + fluopyram fungicides were 0.003, 18.149 and 56.503 µg/mL, respectively. In the detached leaf experiment, the fungicide containing boscalid + pyraclostrobin active substances had the best effect at all doses.