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with cling peach production. The availability and efficacy of chemical thinning programs varies by crop, orchard, and season, therefore hand thinning is often required to adjust crop load for optimal fruit size and quality, and to promote return bloom

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Accurate in-field estimations of crop characteristics can support orchard management and improve packout. Stone fruit ( Prunus sp.) customer satisfaction is greatly influenced by the color and size of fruit, two of the most important fruit

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fit better today's smaller households. Several reports have shown that watermelon growth and yield increase in response to plastic mulch and rowcover, but the effect on fruit size distribution has been overlooked ( Baker et al., 1998 ; Marr et al

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yield of CVS fruit, to increase net income and sustain this commodity-based industry ( Atucha et al., 2013 ; Lovatt, 2013 ; Morales-Payan and Candelas, 2013 ; Sukamto et al., 2014 ). Despite problems of low yield, small fruit size, and alternate

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often found in wild species, along with undesirable fruit attributes like a low level of sugar, high levels of malic acid, undesirable flavors, and small size ( Moing et al., 2003 ). Considering the complexity of breeding an improved peach cultivar that

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sections with low blossom density nonthinned. Three years of research on chemical thinners ( Baugher et al., 2008 ) demonstrated that while the treatments generally increased fruit size, they were inconsistent in reducing follow-up hand thinning requirement

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Many commercially grown stone fruit including apricots (Prunus armeniaca L.), peaches and nectarines [P. persica (L.) Batsch], plums (P. salicina Lindl., P. domestica L.), prunes (P. domestica L.), and pluots (P. salicina × P. armeniaca) have a tendency to produce high numbers of flowers. These flowers often set and produce more fruit than trees can adequately size to meet market standards. When excessive fruit set occurs, removal of fruit by hand thinning is necessary in most Prunus L. species to ensure that remaining fruit attain marketable size and reduce biennial bearing. Over the years there have been numerous attempts to find chemical or physical techniques that would help to reduce the costs associated with and improve efficiencies of hand thinning, however, alternate strategies to hand thinning have not been widely adopted for stone fruit production. In the past 10 years, several chemical treatments have shown promise for reducing hand thinning needs in stone fruit. Management of flowering by chemically reducing the number of flowers has been particularly promising on stone fruit in the Sacramento and San Joaquin Valleys of California. Gibberellins (GAs) applied during May through July, have reduced flowering in the following season in many stone fruit cultivars without affecting percentage of flowers producing fruit. As a result, fruit numbers are reduced, the need for hand thinning is reduced and in some cases eliminated, and better quality fruit are produced. There are risks associated with reducing flower number before climatic conditions during bloom or final fruit set are known. However, given the changes in labor costs and market demands, the benefits may outweigh the risks. This paper reviews relevant literature on thinning of stone fruit by gibberellins, and summarizes research reports of fruit thinning with GAs conducted between 1987 and the present in California. The term thin or chemically thin with regard to the action of GA on floral buds is used in this paper, consistent with the literature, although the authors recognize that the action of GA is primarily to inhibit the initiation of floral apices, rather than reduce the number of preformed flowers. At relatively high concentrations, GA may also kill floral buds. Chemical names used: gibberellic acid, potassium gibberellate.

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Endothall (mono-N,N-dimethylalkylamine salt, 15.9%, endothallic acid 3.8%), ammonium thiosulfate (ATS, 55%), and Wilthin (1-aminomethanamide dihydrogen tetraoxosulfate, 79%) were evaluated over 3 years for use as blossom thinners on mature `Garnet Beauty' and `Red Haven' peaches (Prunus persica). Endothall and ATS were the most effective blossom thinners and reduced set in all 3 years. Wilthin reduced initial set in 2 of 3 years. Hand thinning was reduced by 50% to 80% on endothall and ATS treated trees. The reduction in crop load at bloom resulted in significant increases in fruit size at harvest. We suggest the use of ATS at a rate of 35 to 45 L·ha-1 (3.5 to 5 gal/acre) and endothall at 1.8 L·ha-1 (1.5 pt/acre), applied in 935 L·ha-1 (100 gal/acre) on mature trees. The use of Wilthin at rates higher than 18.6 L·ha-1 (8 qt/acre) may be required for adequate thinning, but phytotoxicity at higher rates was not tested. Other important components for successful blossom thinning include applying materials before the majority of flowers have been pollinated (slightly before full bloom) and to apply the spray when there is very littlewind to assure good coverage and to prevent localized areas displaying increased phytotoxicity.

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The relationship between the number of commercially valuable sized fruit produced per unit land area vs. total number of fruit produced per unit land area for mature navel orange (Citrus sinensis) has not been documented. Knowing this relationship, referred to as the commercial fruit production function (CFPF) within this paper, may aid growers in making fruit thinning and tree pruning decisions and researchers in evaluating the interaction of fruit yield and size in response to fruit thinning, tree pruning, variety selection and tree spacing experimentation. For midseason navel oranges in the southern San Joaquin Valley of California, a reliable CFPF for total annual fruit production ranging from 14,000 to 130,000 fruit/acre was found to exist over multiple seasons in three orchards. The CFPF for two early maturing navel orange varieties was not significantly different with respect to slope or intercept from the CFPF for midseason varieties over the range of 12,000 to 63,000 fruit/acre, but became unreliable when fruit number exceeded 63,000 fruit/acre.

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`GoldRush' is a new scab (Venturia inaequalis) resistant apple (Malus ×domestica) with excellent flavor and storage qualities that tends to produce small and russeted fruit. We investigated the effects of rate, timing, and method of nitrogen (N) fertilizers on `GoldRush' fruit size and quality during 1998-99. Fertilizer treatments were 1) no N fertilizer (control); 2) a low N rate of 45 kg·ha-1 (40.1 lb/acre) applied in April (LN-Apr); 3) a low N rate of 45 kg·ha-1 applied half in April and half in June (LN-Apr+Jun); 4) a high N rate of 90 kg·ha-1 (80.3 lb/acre) split in April and June (HN-Apr+Jun); 5) a high N rate of 90 kg·ha-1 applied in April, May, June, and July at 22.5 kg·ha-1 (20 lb/acre) each month (HN-Apr+May+Jun+Jul); and 6) canopy sprays of 1% (wt/wt) urea-N, equivalent to 7 kg·ha-1 (6.2 lb/acre) applied monthly in May, June, July, and August (foliar urea). In 1998, an additional foliar urea spray at 5% (wt/wt) concentration was applied to trees after harvest. The first year's Ntreatments did not affect relative average fruit weights or total yields, but unfertilized trees produced more fruit in smaller size categories. Nitrogen fertilization resulted in greener and softer fruit both years. In the second year, all N additions increased yields compared with controls, but average fruit weight was inversely correlated with crop load. Foliar urea sprays and HN-Apr+May+Jun+Jul treatments increased yields the most. Fruit from LN-fertilized trees were normally distributed across a range of eight box-count size categories, peaking at size 100 both years. In the unfertilized control, fruit size was skewed into smaller size categories and yield was reduced. Total yields were greatest in foliar urea and HN-Apr+May+Jun+Jul treatments, but fruit-size distribution was skewed into smaller categories, peaking at size 138 in the second year. Foliar urea and HN-Apr+May+Jun+Jul treatments produced the highest crop value, but when estimated labor and fertilizer costs were considered, foliar urea and LN-Apr+Jun were the most efficient treatments. Nitrogen fertilizer improved fruit size and market value, but average fruit size in all treatments remained relatively small in both years, indicating that N fertilization alone may not increase fruit size in `GoldRush.'

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