Effect of 6-BA, NAA and their mixtures on fruit thinning and fruit yield in 'Conference' and 'Blanquilla' pear cultivars

Trials on 'Conference' and 'Blanquilla' orchards were carried out in 2005 and 2007 in the Lleida basin (north-east Spain). Several thinning treatments involving 6-BA and NAA were applied either alone or in mixtures and the results were compared with hand-thinning. In all years, the experimental design was a randomized block. Both bioregulators showed a thinning effect, but this was not statistically significant in all cases. An improvement in fruit thinning was detected when both bioregulators were applied together. In some cases, this effect was too great and resulted in a decrease of around 60% in the final fruit yield, with BA at 150 ppm + NAA at 40 ppm in 'Conference', while in 'Blanquilla', the decrease was of around 30%. There was a direct relationship between fruit weight and crop load and a tendency for fruit weight to increase with 6-BA in 'Blanquilla'.