Controlling white haze disease under in vitro controlled conditions

Epiphytic fungi colonizing the surface of apple fruits have caused severe damages in the last years in Northern Italy. The most important disease called “white haze” is cause by the agent Tilletiopsis sp. and consists of a thin whitish to gray layer of fungal growth sticking to the cuticle of apple surface. The fungal growth may increase rapidly during the summer and harvest time but no evidence of new symptoms and spread from infected to healthy apples was observed during storage. In vitro test with different chemical fungicides and new natural compounds were performed during 2020 and 2021 to determine their capability to reduce the fungal growth on Petri plate and design new effective control strategies in the field trial. Furthermore, the effect of UV-C treatment in reducing the growth of Tilletiopsis sp. in Petri plate was investigated. Results indicate the efficacy of chemical fungicide application ranged between 4 to 100% with the full control obtained by fosetyl-Al, captano, dodine and penconazole at 20°C on PDA media. Interestingly, a full control of the pathogen was also obtained with a new natural compound based on orange oil but several others showed an acceptable control such as potassium bicarbonate, potassium phosphonate and acid clays, while UV-C treatment did not inhibit the fungal growth of the pathogen at the tested conditions