Foliar boron increases berry number and yield of two highbush blueberry cultivars in Missouri

Foliar applications of boron (B) have been shown to increase fruit set and yield of several woody fruit species, but there have been no reports of foliar B effects on blueberry (Vaccinium corymbosum L.). The objective of this study was to determine if foliar B would decrease tip dieback, alter yield components, and increase berry yield of blueberry. Blueberry plants (cvs. Collins and Blueray) were grown on a Menfro series soil (fine-silty, mixed, mesic Typic Hapludalf) with the two cultivars planted in alternate rows. Five uniform plants from each row were either treated with foliar B plus surfactant or untreated. Foliar B was applied in the fall prior to each harvest year, 1990 through 1993, and additional foliar B was applied in the spring in 1991 through 1993. Foliar B increased blueberry weight/plant by 10% over the four-year period. The increase in blueberry yield was a result of a 12% increase in number of berries/plant. Yield increase following foliar B treatment was greatest during the first two weeks of harvest for Collins and during the second two weeks for the later flowering Blueray. Following a freeze (-8 degrees C) at flowering in March 1990, tip dieback for Collins was 75% greater in control plants than for plants treated with foliar B the previous fall. The reduced tip dieback in 1990 following foliar B treatment resulted in the largest percent increase (31%) in blueberry yield during the four-year study. However, the actual yield increase in 1990 of 201 g/plant was very similar to the four-year average increase of 238 g/plant with foliar B treatments. When the yield increase per plant is multiplied by the number of plants typically grown on a hectare of land (2500), it is apparent that foliar B applications for Collins and Blueray blueberries in the Midwest would be profitable.