The combined effects of thermal pruning, fungicide and fertilizer applications on lowbush blueberry

Abstract

Wild lowbush blueberries (Vaccinium angustifolium Ait. and Vaccinium myrtilloides Michx) yields are highly variable since they depend on several factors, some of which can be influenced by growers with different agricultural practices. The primary objective of this research was to evaluate the effects of three key management practices on the yield of lowbush blueberry, as well as on related variables, including the number and height of stems, the nutrient status of the plants, and the presence of crop pests. Over four years, twelve combinations of three practices were tested and replicated four times at two sites in Normandin (Quebec, Canada). The practices included: i) type of pruning (mechanical or thermal), ii) use of fungicide (with or without), and iii) application of fertilizer (mineral, organic, or none). Thermal pruning did not enhance fruit yield or any other evaluated parameters compared to mechanical pruning. Throughout the years, fungicide applications caused a yield gain of about 212 kg ha-1 yr-1, a decrease in disease rate (Sphaerulina leaf spot), and an increase in stem density when combined with mineral fertilizer. Mineral fertilizer also reduced the incidence of Sphaerulina leaf spot, improved the plant nutrient status, and caused a gain in yield of about 853 kg ha-1 yr-1. Organic fertilization improved fruit yield by about 691 kg ha-1 yr-1. Finally, the results indicated that applying fungicide increased the export of macronutrients in harvested fruits, highlighting the necessity for long-term monitoring of nutrients.