Branched Secondary Alcohol Ethoxylate, Ammonium Thiosulfate, Calcium Polysulfides-Thiosulfate, and Fish Oil Effects on Blossom Thinning, Fruit Set and Quality of Peaches and Nectarines

Total crop load has an inverse relationship with fruit size, while larger fruit size is often demanded by the peach and nectarine markets. Hand-thinning is extremely expensive, and thus, crop load adjustment, using blossom thinners is a crucial practice to ensure production of commercially acceptable fruit size and yield efficiency in stone fruit. In this study, the influence of branched secondary alcohol ethoxylate (Tergitol TMN-6) and/or ammonium thiosulfate (ATS), Crocker Fish Oil (FO), and a mixture of calcium polysulfides and thiosulfate (lime sulfur) on fruit set and quality attributes in peaches (Prunus persica) and nectarines (P. persica var. nectarina) were studied. All blossom thinners reduced fruit set in “Summer Lady” peach in both 2016 and 2017. Fruit sets in “Summer Lady” peach trees with a double application of Tergitol TMN-6 at the rate of 7.5 or 10 mL ·L¯1, each rate applied at 40% and 80% bloom, were lower than those receiving the same rates of this chemical only at 80% bloom, but they were similar to those receiving a single Tergitol TMN-6 spray at 15 mL·L¯1 at 80% or 100% bloom. “Summer Lady” peach trees receiving FO at 20 mL·L¯1 plus lime sulfur at 25 mL·L¯1, once at 40% bloom and again at 80% bloom had lower fruit set as compared to Untreated Control but the fruit set was higher than those with any Tergitol-TMN-6 spray. Tergitol TMN-6 at 12 m·L¯1 at 100% bloom or 10 mL·L¯1 all stages of bloom reduced fruit set in “Zee Lady” and “Snow Giant” peaches. In “Snow Giant” peach, trees receiving Tergitol TMN-6 at all concentrations and blossom stages had significantly higher fruit weight as compared to the trees of Un-treated Control. Applications of Tergitol TMN-6 at all concentrations at 80% bloom reduced fruit set in “Red Globe” and “Elberta” peaches in Utah. ATS and FO slightly reduced fruit set in peaches but they were less effective than Tergitol TMN-6 in all cases. Overall, it is concluded that efficacy of blossom thinners depends on the rate of thinners, temperature, cultivar and stage of bloom development.

Application of NAA and BA in Chemical Fruit Thinning of Autochthonous Cultivars of Apple

The paper presents the fruit thinning response to NAA and BA plant regulators of autochthonous cultivars of apples. The experiment was designed to evaluate NAA, over a range of concentrations （15, 20 and 30 ppm） when applied alone, and BA ＋ NAA combinations （BA--60, 100, 120 or 140 ppm ＋ NAA 5 ppm） for thinning the assessed apple cultivars. All the applied treatments with NAA and BA ＋ NAA adequately thinned ＂Senabija＂ and ＂Ko2ara＂, whereas application of NAA 20 ppm and 30 ppm and combined treatment BA 140 ppm ＋ NAA 5 ppm were effective fruit thinners for ＂Pasinka＂. In terms of the average fruit weight and number of fruits categorized as large （〉 75 mm or 〉 65 ram）, as well as from the aspect of fruit number per trunk cross-sectional area, the variant of treatment BA 140 ppm ＋ NAA 5 ppm was most effective on ＂Senabija＂ and ＂Paginka＂, whereas BA 100 ppm ＋ NAA 5 ppm had the best effect on ＂Kozara＂.