Die-back of apricot trees following soil application of boron

Abstract

Abstract Die-back and other symptoms consistent with those of boron toxicity developed in spring 1980 and 1981 in 70 and 39% respectively of Sundrop apricot trees that had been given about 2.4 g per tree of B as borax when they were planted in a commercial block in 1978. Trees of the same variety planted in adjacent rows in 1979 which had not received B grew well. Analyses of 13 major and minor elements in buds, leaves, bark, and fruits from both groups of trees showed no consistent differences between the 2 groups of trees except in tissue B levels. B concentrations were highest in buds, with a similar pattern of change occurring during the dormant period in both healthy and unhealthy trees. In spring 1981, buds on unhealthy trees which failed to break contained 40-100 μg/g dry matter (DM) (average 82.3 μg/g DM) B, whereas buds from similar positions on healthy trees not receiving B contained 23-43 μg/g DM (average 37.0 μg/g DM) B. Replant Moorpark apricot trees in another commercial orchard, given great...