Biological Control of Botryosphaeria Dieback of Grapevines in British Columbia, Canada

Background and goals Botryosphaeria dieback is a grapevine trunk disease responsible for significant economic losses to grape producers worldwide. There are currently no products registered in Canada to control grapevine trunk diseases, and sustainable production has become a focus of the Canadian grape and wine industry. Therefore, the objectives of this research were to evaluate locally sourced Trichoderma spp. as biocontrol of Botryosphaeria dieback fungi in the field, to compare Trichoderma spp. against commercial products registered in other countries, and to determine optimum temperatures for conidial germination of Trichoderma spp. found in British Columbia (BC).

Methods and key findings Detached cane assays under greenhouse conditions and field trials in a Merlot vineyard during two growing seasons assessed Trichoderma spp. from BC and commercial products as pruning wound protectants against Diplodia seriata and Neofusicoccum parvum over time. The Trichoderma-based treatments developed in this study provided pruning wound protection for up to 60 days after treatment and performed better or similarly to commercial products. Germination studies showed conidia of Trichoderma canadense germinated faster at lower temperatures than the other Trichoderma spp.

Conclusions and significance This represents the first study evaluating locally sourced Trichoderma spp. as protection against grapevine trunk disease fungi under field conditions in Canada, and shows the potential that these endophytic isolates have as pruning wound protectants over time. This study also screened commercial products to manage grapevine trunk diseases for the first time in Canada, providing key data to support product registration. The discovery of faster conidial germination of T. canadense at lower temperatures deserves further investigation, as this species could be better adapted and thus provide more effective pruning wound protection when applied at the colder temperatures experienced in BC during the pruning season.