Cytokinin for Chemical Fruit Thinning of Asian Pears

Asian pear fruit price and quality are closely associated with fruit size. Large fruit are highly desired and bring excellent market price. In most years heavy fruit set in Asian pears requires expensive hand thinning to reduce crop load enough to obtain optimum fruit size. Effective chemical thinners are urgently needed by Asian pear growers. Experiments were conducted to evaluate a cytokinin (6-benzyladenine formulated as MaxCel) as a chemical thinner for Asian pears. The experiments were conducted in commercial orchards in New Jersey in 2007 and 2008. Spray applications of MaxCel at 0, 200, or 250 ppm were applied at 12 mm average fruit diameter to ‘Hosui’ (in 2007) and ‘Kosui’ trees in Northern New Jersey and at 0, 50, 100, 150, 200, and 250 ppm to ‘Hosui’ (in 2008), ‘Shinko’, and ‘Yoinashi’ trees in Southern New Jersey. Treatments were applied in 100 GPA of water at 80 PSI with a handgun sprayer. In both experiments in Northern New Jersey the 200 and 250 ppm treatments reduced fruit set significantly but, 200 ppm was not different from 250 ppm. In Southern New Jersey, where crop load was much less, significant thinning was only obtained with 250 ppm and only in one cultivar (‘Yoinashi’). Time required for follow-up hand thinning to adjust crop levels was significantly decreased only in the experiments in Northern New Jersey. Time required for hand thinning was significantly reduced in ‘Hosui’ trees treated with 250 ppm and in ‘Kosui’ trees treated with either 200 or 250 ppm. MaxCel can be an effective a chemical thinner for Asian pears.