Winter injury of red raspberry ( Rubus idaeus L.) buds under commercial field conditions: Relationships with temperature, spur blight and biochemical traits

Winter injury limits raspberry ( Rubus idaeus L.) production in northern climates. This study evaluated the associations between winter injury, temperature, spur blight severity, and bud proline and soluble sugars contents in ‘Glen Ample’ raspberry grown in eight commercial plantations in Estonia over three winters: 2021/22, 2022/23, and 2023/24. Bud injury ranged from 18 to 98% among plantations and years, while neither minimum temperature nor the maximum number of consecutive hours below −25 °C accounted for this variation. A significant positive correlation was found between spur blight ( Xenodidymella applanata ) severity and winter injury ( r = 0.833). Proline and soluble carbohydrate levels in March were not consistent indicators of bud winter survival. These findings demonstrate that winter injury of raspberry buds is determined by interacting abiotic and biotic stress factors rather than by minimum temperature alone and growers should consider cane health alongside winter temperature in winter-injury risk assessments.