Field and in vitro sensitivity of Valsa ceratosperma (Cytospora vitis) to fungicides

The occurrence of Valsa ceratosperma (Tode ex Fr.) Maire, causal agent of Valsa canker, was reported for the first time as a pathogen on pear in the Emilia Romagna region (Italy) in 2001 and since then the disease incidence has greatly increased. Valsa canker is one of the most important diseases of apple orchards in China, Japan and Korea where preventative good farming and chemical treatments (especially with SBIs and benzimidazoles) are the best way to try to control the disease on pear. In order to investigate the possibility of chemical disease control, tests in vitro (mycelial growth on PDA) and a field trial were carried out. SBIs, benzimidazoles, strobilurins, dicarboximides, tolylfluanid, fluazinam, fludioxonil, cyprodinil, dithianon, mancozeb and captan were tested in vitro assays. Some of the formulated compounds used in in vitro assays were applied in the field trial. All fungicides tested in vitro were more or less active; SBIs, benzimidazoles, fludioxonil, fluazinam and iprodione showed the best effectiveness. No activity was shown by any of the products in the field trial, probably because they are not able to penetrate through the bark and reach the pathogen in the cortical tissues and phloem.