Impact of frost injury incidence at nodes of Pinot Noir on fruitfulness and growth‐stage lag

Background and Aims Spring frosts can injure primary buds and young shoots and stimulate secondary shoot production in Vitis spp. The aim of this study was to develop methods to quantify yield and phenology effects of frost injury during budburst. Methods and Results Eight hundred and sixty‐nine nodes from 92 half‐vines of Pinot Noir in eight blocks from four Tasmanian vineyards were sampled; 15–92% of shoots per half‐vine were injured after a sub‐zero air temperature ≥ −4.5°C. Severity of frost injury was spatially variable among vines both with and without frost protection. Generalised linear mixed models revealed that node injury was associated with a mean 27‐fold increase in the odds of >1 shoot per node. Mean December scores for modified Eichorn–Lorenz growth stage were 18.9 and 17.2 for nodes with one shoot and >1 shoot, respectively. The probability of healthy and injured nodes producing fruit was 0.81 and 0.69, respectively. In a season with poor fruitset, the estimated difference in yield per linear m of row between 0 and 100% incidence of injured nodes was 0.2 kg. Conclusion Assessment of the incidence of frost injury and fruit mass per node was sufficient to estimate the impact of injury on yield at the vine and block level. Significance of the Study Future studies are expected to benefit from application of these efficient sampling, assessment and statistical methods to determine the site‐specific impact of early spring frost injury on fruitfulness and growth‐stage lag.