Post petal fall applications of gibberellins improve fruit set on pear

Abstract

Commercial pear production has become increasingly difficult over the last decade, with low fruit set being one of the main factors leading to poor yield of pear orchards. The use of gibberellins to increase fruit set has been widely reported, but in most of the cases these applications are made at full bloom or right after a spring frost has occurred. However, the increase in fruit set due to early applications of gibberellins such as at full bloom is often lost at June drop. Aim of this study was to assess dose and timing of different gibberellin applications made after petal fall to improve the final fruit set in pear orchards. Four experiments were conducted during four years (2010–2013) in mature pear orchards with ‘Conference’ as the scion cultivar. Fruit set and yield were increased when gibberellins were applied after petal fall, with a positive relationship with dose. Applications of GA4+7+BA tended to promote higher fruit set and yield than GA3, and in addition, they were less dependent to the moment of application. GA4+7+BA showed an additive effect when performing multiple applications. Return bloom was slightly affected when gibberellins were applied after petal fall. The strategy that showed a better behavior to increase fruit set was GA4+7+BA at 500 mL·ha−1 at H + 14, which coincides with the weeks of the natural fruit drop.