Transient Heat Therapy Has Few Effects on Grapevine Performance in the Okanagan Valley, British Columbia, Canada

Goals The goal of this study was to evaluate a commercially available machine (Agrotherm XT™, Agrothermal Systems^®, Napa, CA) for transient heat application as a means of enhancing vineyard canopy temperatures during the growing season and to study the effects of transient heat application on grapevine performance, phenology and berry quality. The study was conducted over two growing seasons in three vineyards located in East and West Kelowna in the Okanagan Valley in British Columbia, Canada.

Key Findings

• Transient heat application is not an effective management practice

• Results were not consistent among vineyard locations nor growing seasons.

• In 2019 only, treated Merlot vines had fewer berries per cluster but higher juice pH.

• In 2019, treated Chardonnay 2 vines had reduced leaf greenness but higher pruning weight.

• In 2020 only, treated Merlot vines had reduced leaf greenness but higher pruning weights.

• In 2020, treated Chardonnay 2 vines had reduced leaf greenness but higher berry weights and soluble solids.

• In 2021 only, treated Chardonnay 2 vines had higher fruitfulness (clu/sh).

Impact and Significance Heat treatment did not have consistent effects on grapevine performance and berry quality, and no changes in grapevine phenology were observed. Given the high purchase costs, transient heat therapy is not an effective management strategy to improve grapevine performance and berry quality in the north central part of the Okanagan Valley in British Columbia.