Evaluation of fungicide efficacy against Neofusicoccum species causing dieback disease of blueberries in New Zealand

Several Botryosphaeriaceae species have been reported to cause stem canker, twig blight and dieback of blueberries, with different species being reported in different parts of the world. Pruning wounds are regarded as primary infection sites for these pathogens. This research evaluated in vitro and in vivo efficacy of fungicides against the main Neofusicoccum species associated with blueberry dieback in New Zealand. In vitro evaluation showed that four out of the nine fungicides tested were effective at reducing mycelial growth and/or conidial germination and germ tube growth of three pathogenic isolates each of N. australe , N. luteum , N. parvum and N. ribis . In vivo evaluation carried out with fungicides on wounded and non-wounded plant tissues on potted and field blueberry plants showed that carbendazim and tebuconazole were the most effective for protecting blueberry plants from infection by Neofusicoccum species. This research showed the importance of protecting both wounded and non-wounded tissues, with more than one application of fungicides likely to be required to provide effective control of the disease under natural inoculum levels.