CHEMICAL THINNING OF CLING PEACH

S.M. Southwick, K.G. Weis, J.T. Yeager, M.E. Rupert, J.K. Hasey
Cling peaches bear large crops and thinning is typically used to increase fruit size, reduce limb breakage and insure adequate return bloom for next season. Hand thinning is costly and requires a dependable, adequate labor force for a specific and limited time. Chemical thinning, if effective and safe, could make fruit thinning more efficient and help to reduce costs. We tested the efficacy of four chemicals in California in 1996 for their potential as thinners on 'Loadel' cling peach [Prunus persica (L.) Batsch]. Whole tree sprays of Endothall® (Elf-Atochem, Inc.), Wilthin® (Entek, Inc.), and Armothin® (Akzo-Nobel, Inc.) were applied by commercial orchard sprayer during bloom in 1996; Release LC® (Abbott Laboratories, Inc.) was applied at regular intervals during June/July 1995 at approx. 23 g/935 l/ha. Armothin® (3% at 935 l/ha or 1870 l/ha carrier rate) was applied at 60% of full bloom (FB). Wilthin® treatments were applied at 75 – 80 % FB at rates of 3.78 l + 0.96 l Regulaid, 5.68 l, and 5.68 l + 0.96 l Regulaid per 935 l/ha. Endothall® was applied at 80 – 100% FB, and a single treatment was applied as a split application at 40 – 60% FB and 80 – 100% FB. Rates applied were 0.9 l, 1.2 l, 1.2 l x two applications, and 1.8 l per 935l/ha. Of the four products tested in 1996, Release LC® proved to be the most effective thinning agent. Treatment with Release LC® in late June 1995 resulted in significantly better size and weight in salable fruits in 1996 than that of the untreated control as the yield of undersized fruits was decreased by treatment and the time to thin was reduced by 55% of that required in the untreated, hand thinned control. Success of Endothall®, Armothin®, and Wilthin® in 1996 may have been compromised by rainy weather during bloom and the extended bloom in 1996 resulting from very low accumulation of chilling hours. Ongoing research in 1997 reevaluates Endothall®, Armothin®, and Wilthin®, and return bloom with Armothin®.
Southwick, S.M., Weis, K.G., Yeager, J.T., Rupert, M.E. and Hasey, J.K. (1998). CHEMICAL THINNING OF CLING PEACH. Acta Hortic. 465, 647-654
DOI: 10.17660/ActaHortic.1998.465.81
https://doi.org/10.17660/ActaHortic.1998.465.81
Prunus persica, fruit thinning, gibberellin, chemical thinning, plant growth regulation, plant growth regulators, surfactant, bloom thinning

Acta Horticulturae