Abstract
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 ·Lˉ1, 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·Lˉ1 at 80% or 100% bloom. “Summer Lady” peach trees receiving FO at 20 mL·Lˉ1 plus lime sulfur at 25 mL·Lˉ1, 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·Lˉ1 at 100% bloom or 10 mL·Lˉ1 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.
Highlights
Hand-thinning is a critical cultural practice that increases the leaf-to-fruit ratio and leads to the production of larger fruit size in apples and peaches, as well as reduction of the biennial bearing in apples [1] [2] [3] [4]
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
The goal of this study was to determine efficacy of Tergitol TMN-6, lime sulfur, ammonium thiosulfate, and fish oil on blossom thinning, fruit quality, and yield in different peach and one nectarine cultivars under conditions of southwest, USA
Summary
Hand-thinning is a critical cultural practice that increases the leaf-to-fruit ratio and leads to the production of larger fruit size in apples and peaches, as well as reduction of the biennial bearing in apples [1] [2] [3] [4]. Dormex was found to be an effective blossom thinner for plums [6] and peaches [2] in Idaho. Full-bloom applications of Dormex at 2.5 to 3.12 mL∙L−1 significantly reduced fruit set in “Flavorcrest” peach [7]. In field trials in Washington, California, and Idaho, Endothall was an effective blossom thinner for apples and stone fruit [2] [8]. On “Friar” plum, full-bloom application of Wilthin at 10 mL∙L−1 plus polyoxyethylenepolypropoxypropanol (Regulaid with 90.6% a.i) at 1.25 mL∙L−1, using a hand-gun sprayer, increased the fruit size [4]. Full-bloom application of the surfactant N, N-bis2-(omegahydroxypolyoxyethylenepoly-oxypropylene) ethyl alkylamine (Armothin) at 30 mL∙L−1 or 5 mL∙L−1 reduced fruit set in “Loadel” peach in California [11]
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