ARS | Publication request: Chemical and Mechanical Thinning of Peaches

Submitted to: New England Vegetable and Fruit Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: January 4, 2008
Publication Date: April 1, 2008
Citation: Baughner, T., Schupp, J., Miller, S.S., Harsh, M., Lesser, K., Reichard, K., Sollenberger, E., Armand, M., Kammerer, L., Reid, M., Rice, L., Waybright, S., Wenk, B., Tindall, M., Moore, E. 2008. Chemical and Mechanical Thinning of Peaches. New England Vegetable and Fruit Conference Proceedings.

Technical Abstract: Horticultural and economic evaluations of chemical blossom thinners were conducted in 16 commercial orchard trials from 2005 to 2007. The treatments were applied at 80 percent full bloom and compared to hand thinning post-bloom. Chemical efficacy was variable among years and blocks. Chemical thinners decreased follow-up hand thinning time in 33 percent of the trials and increased fruit diameter in 55 percent of the trials, resulting in net impacts of $14 to $983 per acre in 78 percent of the trials. Similar evaluations of two mechanical thinners were conducted in four commercial peach orchard blocks in 2007. A mechanical blossom thinner designed by a German grower for thinning apple trees in organic orchards was tested on peach trees trained to either a perpendicular V or quad V system. Thinning was conducted at 20 or 80 percent full bloom. A USDA spiked-drum shaker, originally designed for harvesting citrus, was included in the orchard tests at 45 days after full bloom. Mechanical thinners reduced fruit set, decreased follow-up hand thinning time, and increased the number of fruit in the 3-inch or greater size distribution in 100 percent of the trials. Net profits ranged from $71 to $796 per acre. Bloom thinning at 20 percent full bloom was similar to thinning at 80 percent full bloom. Detailed flower counts on branches with different orientations indicated that pruning may be adjusted to improve thinner performance.