Fungicides can inhibit mycelial growth but not protect against Ceratocystis fimbriata infection via pruning wounds on kiwifruit vines

Abstract Ceratocystis wilt, caused by Ceratocystis fimbriata, is the primary disease affecting kiwifruit (Actinidia spp.) and a major constraint for its cultivation and expansion in Brazil. Additionally, it poses a potential threat to other major kiwifruit-producing countries, such as China, New Zealand and Italy, where the disease has not reported on kiwifruit yet. In kiwifruit vines, the infection generally initiates through the roots, but pruning wounds can also serve as an entry point for the pathogen. Currently, there is a dearth of proven effective strategies for controlling this disease, and there is no information on the effectiveness of fungicides for preventing the disease. In the present study, we evaluated the efficacy of four fungicides: metalaxyl + mancozeb, boscalide + cresoxim-methyl, pyraclostrobin, and copper hydroxide, against C. fimbriata isolates. We found that metalaxyl + mancozeb and pyraclostrobin were the most effective in inhibiting mycelial growth in vitro. However, when evaluated as wound pruning protectors in two kiwifruit cultivars, these fungicides were not effective. The results found in the in vitro assays can serve as guides for the development of chemical control of Ceratocystis wilt in kiwifruit. Furthermore, as none of the fungicides tested here were effective in protecting pruning wounds against C. fimbriata infection in kiwifruit vines, it is interesting that other active ingredients or application methods are evaluated in further studies.