Abstract
Sevin was used in thinning sprays in dilute—1x—and concentrate form—ranging from 3X to 33X —over a 4-year period on mature ‘Rome Beauty’ apple trees. Although treatments were not the same in each year, all sprays applied significantly thinned in 3 out of 4 years. There was some evidence that concentrate sprays thinned less than dilute sprays, but usually not significantly so. When using 33X concentrates, significant thinning was achieved in 1 year when Sevin was used at full strength—33 lb./100 gal. Approximately the same degree of thinning was obtained when the rate was reduced by one-half. Adding pesticides commonly used in petal-fall sprays to Sevin—all concentrated to the same extent—did not alter significantly the thinning obtained with Sevin alone.
Results on ‘Jonathan’ apples in a 1-year experiment revealed significant thinning with NAD and Sevin in a dilute spray, as well as Sevin at 3X and 6X concentrates. In a 1-year experiment on ‘Golden Delicious’, NAA thinned significantly as a dilute spray, and at 3X and 6X concentrates. The dilute spray was more effective.
Early thinning reduces competition among fruit, which increases fruit cell division and size potential ( Lakso et al., 1996 ). Although existing chemical and mechanical blossom thinners may reduce the apple fruit set, blossom thinners are
Studies were conducted on peach [Prunus persica (L.) Batsch] during 1988 to 1990 to test the performance of a tree-width rope-curtain bloom thinner and a rotating rope-curtain thinner. Six trips over the tree canopy were required with the tree-width rope curtain, and only one trip was required with the rotating curtain to thin to a spacing of about one flower per 9 cm of fruiting shoot length. Based on the number of flowers per square centimeter of branch cross-sectional area (CSA) immediately following thinning and the number of fruit per square centimeter of CSA following June drop, rope-curtain thinning was equal to hand-thinning at full bloom (FB). Rope-curtain thinning reduced hand-thinning time by 40% and increased harvest fruit weight by 10% to 20%. Research on various modifications in tree training/pruning indicated that performance of the mechanical thinner was negatively correlated with shoot density. Thinning was maximum on open-center-trained trees on which detailed pruning had been conducted to eliminate overlapping shoots.
An analysis of daytime high temperatures for the 10-year period from 1984 to 1993 indicated that, in the 21 days after full bloom (AFB) in 7 of 10 years, there were 3 days or more above 29.5C. In the 15- to 21-day period AFB, when fruit are considered at their optimum diameter (8 to 12 mm) for thinning, only 3 days above 29.5C were recorded. In the 15 to 21 days AFB, the high temperature was only 24C for 7 out of 10 years. Thus, growers would have to spray at temperatures 5.6C degrees lower if they were to choose to spray the warmest 3 days during the 15- to 21-day period when fruit are 8 to 12 mm in diameter. NAA caused thinning of `Golden Delicious' fruit at 8-mm fruit diameter. Tank mixing of one of several pesticides (regulaid or guthion, captan, carzol, imidan, polyram, lorsban, omite, or lannate) had no effect on NAA efficacy. Comparison of identical chemical thinning treatments (carbaryl + Accel + oil) applied to `York' and `Red Delicious' apple trees indicated that more thinning occurred with the PF treatments than at 8 mm. Average 2-day high temperatures at PF were 7.1C higher at PF for the `Red Delicious' experiment and 5.6C higher for the `York' experiment. The higher temperatures at PF could account for the differences in thinning response and not the spray timing. Pollination and fertilization inhibitors caused some fruit thinning at the highest rates and multiple applications. The MYX4801 caused more thinning and more injury to fruit than other materials. Endothall gave good thinning without fruit injury. Wilthin (GWN-6592) did cause some thinning, but fruit injury was a problem in one experiment.
, soil conditioning, and crop thinning, in cool and hot–warm climates ( Bavaresco et al., 2008 ; Bledsoe et al., 1988 ; Keller et al., 2005 ; Reynolds et al, 1996 ; Sadras and McCarthy, 2007 ). However, climate often influences cultural treatments and
Abstract
Airblast spray applications of ammonium thiosulfate (ATS) were made to individual peach trees in a single row or to small blocks 5 rows wide and 10 trees long to determine if drift from adjacent rows increased bloom thinning. Increased flower thinning was found in the center row of the 5-row-wide-block when compared by regression analysis to applications made to trees in a single row. Ethylene-bisdithio-carbamate (Zineb 78WP) was used to determine the amount of spray deposit contributed by airblast sprays to adjacent rows. Airblast spraying of peach trees in full bloom contributed chemical deposits to peach flowers in the adjacent row equal to 43% of that deposited on the sprayed row, and 26% to the second row removed.
Abstract
Sprays of various concentrations of Fruitone, a commercial formulation containing 2-(3-chlorophenoxy)-propionamide and 2-(3-chlorophenoxy)-propionic acid (3CPA) or of 2-chloroethylphosphonic acid (Ethrel) were applied to ‘Early Amber’, a short cycle (70 days), low-chilling (300 hours < 45 F) peach grown in Florida. Adequate thinning of fruits was obtained from treatments during the 4-day interval that the endosperm was changing from the free nuclear to the completely cellular stage. The most satisfactory concn of 3CPA and Ethrel for fruit thinning were 300 and 30 ppm, respectively. All concn of 3CPA and Ethrel which caused fruit thinning also increased ethylene concn in the fruit.
Influence of various concentrations of hydrogen cyanamide (HC) on fruit thinning of `Rome Beauty' apple (Malus domestica Borkh.), `Friar,' and `Simka' plums (Prunus salicina Lindley) were studied. A full bloom application of HC at all tested concentrations decreased `Rome Beauty' apple fruit set and yield, and increased fruit weight. Hydrogen cyanamide at 0.25% (V/V) resulted in adequate apple thinning, indicated by the production of an ideal fruit weight. Prebloom and full bloom applications of HC at greater than 0.75% reduced plum fruit set and yield in `Friar.' Full bloom application of HC at 0.25% to 0.50% showed a satisfactory fruit set, yield, and fruit size in `Friar' plum. Full bloom application decreased fruit set and yield in `Simka' plum. Hand thinning, as well as chemical thinning, is recommended for plums.
A decision support system has been developed to help Colorado fruit growers with apple (Malus domestica Borkh.) thinning. This system can also be used as a teaching aid and as a tool for generating research hypotheses. The system determines if fruit thinning is needed by identifying catastrophic events that would eliminate the need for thinning. The major function of this decision support system is determination of tree responsiveness to chemical thinning agents. This is accomplished through analysis of the user's answers to questions related to the physiological status of the trees, environmental data, bearing history, and the apple variety in question. On the basis of the above analysis, two sets of recommendations are presented: general recommendations based on the variety selected, and specific ones for that variety based on growth stage and tree responsiveness to thinners. The user also is provided with the rationale for the recommendations.
Postbloom applications of benzyladenine (BA) thinned young fruitlets of mature `Empire' apple trees (Malus domestica Borkh.) as well as or better than NAA or carbaryl (CB). BA increased fruit weight more effectively than either NAA or CB. Promalin (PR) was less effective than BA for both thinning and fruit-weight increase. In 1990, both BA and PR reduced fruit set up to 29 days after full bloom, but PR showed less thinning activity. BA and NAA produced independent and additive thinning responses when tank-mixed. Effects of all thinners on foliar mineral-nutrient concentrations were associated with changes in fruit load. BA increased return bloom as much or more than NAA or CB. PR did not affect return bloom. Chemical names used: N -(phenylmethyl)-1 H -purine-6-amine [benzyladenine (BA)]; BA plus gibberellins A, and A, [Promalin (PR)]; 1-naphthaleneacetic acid (NAA); 1-naphthalenyl methylcarbamate [carbaryl (CB)].