Are fungicides effective in protecting pruning wounds against Ceratocystis wilt on kiwifruit vines?

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, the disease poses a threat to other major kiwifruit-producing countries, such as China, Chile, New Zealand, and Italy, where the disease has not been reported on kiwifruit vines 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 C. fimbriata infection on kiwifruit. 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 evaluating these fungicides as pruning wound protectors in two kiwifruit cultivars, these fungicides were not effective, in the method tested. The results found in the in vitro assays can guide 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, other active ingredients or application methods must be evaluated in upcoming studies.