Active thermography to determine grape bud mortality: system design and feasibility

Abstract

Context and purpose of the study – Bud death due to cold damage is a recurrent and major economic issue with Vitis vinifera L. in the Northeastern U.S. winegrowing regions. Primary buds – and sometimes secondary and tertiary buds – are often damaged by fluctuating temperatures in the winter and early spring. To maintain balanced vegetative and reproductive growth of a vine, pruning practices need to be adjusted to account for bud damage. Conventional bud damage assessment requires growers to sample canes/spurs, cut nodes with a razor blade, and then visually assess bud damage. This process is laborious and becomes a major barrier for damage-compensated pruning decision-making, leading to too few live buds per vine and the associated excessive vigor and low yield that result. The overarching goal of this study was to develop an active thermographic system for non-destructive detection of bud damage in the vineyard.

Material and methods – An active thermographic system was developed by integrating a thermal camera, heating stimulation, and sample holder. A custom computer program was developed to synchronize the camera and heating unit to acquire a thermal image sequence of a grapevine cane under a predefined heating stimulation. The heating stimulation included an artificial heating phase using a set of heating lamps and a natural cooling phase. Regions of interest (ROIs) were selected for grape buds to extract thermal responsive curves between damaged and healthy buds.

Results – Results demonstrate that significant differences were observed in thermal responsive curves between damaged and healthy buds for all five representative cultivars used in this study. This lays a solid foundation to further establish classification models to differentiate grape buds with different mortality status effectively.