Southwick, Stephen :

Glozer Dr, Kitren

Hasey, Janine K

Hansen, Randy :

Use of Preharvest Gibberellin and ReTain Sprays to Improve Fruit Firmness of â?? Andross â?? and â?? Ross â?? Cling Peach , 2003 1 1 2 1 Stephen Southwick , Kitren Glozer , Janine Hasey and Randy Hansen 1 Department of Pomology , University of California , One Shields Avenue , Davis , CA 95616 2 University of California Cooperative Extension , Sutter / Yuba Counties , CA Keywords : Prunus persica , gibberellin , plant growth regulation , plant growth regulators Summary : Treatment in 2002 with GA ( Pro - Gibb 4 % , Valent Biosciences Corp . , Libertyville , Illinois , USA ) significantly 3 improved the firmness of â?? Andross â?? cling peach in 2002 . Spray concentrations of both 20 and 32 g Pro - Gibb + 0.1 % Regulaid per 100 gallons per acre were effective . GA sprays of 20 g / acre were most effective when applied about 12 days before harvest and 32 g / acre were most effective when applied about 4 weeks before harvest . GA sprays of 20 g / acre applied either 3 or 4 weeks before harvest on â?? Andross â?? improved firmness on the second pick . The higher GA concentration applied at 3 and 4 weeks before harvest led to a slight delay in harvest of â?? Andross â?? . GA sprays did not affect fruit drop . Similar GA treatments on â?? Ross â?? did not improve firmness when compared with the control . ReTain applied at 50 g a.i . / acre at 8 days before harvest did not improve firmness or reduce fruit drop on â?? Andross â?? or â?? Ross â?? . GA sprays from 20 to 40 g / acre applied at 7 days or less before harvest in 2001 resulted in an overall increase in firmness at harvest , and a better retention of firmness over a storage period than was found in the untreated control in â?? Andross â?? . No difference in return bloom was found for GA treatments made in 2001 or 2002 . In 2003 , we repeated these experiments with some changes . As before , we used both â?? Andross â?? and â?? Ross â?? cultivars and the plant growth regulators ProGibb ( gibberrellin A at 20 and 32 g a.i . per acre ; gibberllic acid ) and 3 ReTain ( Valent BioSciences ; 50 g a.i . per acre ) . Firmness of â?? Andross â?? peach was increased by GA sprays of 32 g / acre applied approximately 3 weeks before harvest on fruit harvested on July 31 ( first harvest ) . These fruit maintained improved firmness compared to the control for 21 hours after harvest , and were as firm as the control after 5 days . Fruit treated with 20 g / acre GA on 9 July were numerically firmer than the control fruit after harvest and throughout storage , although not statistically firmer . Fruit treated at 32 g / acre of GA on 16 July were equal to the control at harvest but grew less firm than the control with extended storage . Percentage of undersized fruit , number of fruit that dropped cumulatively , and weight per fruit were not different among treatments at the first harvest . The number of external bruises per fruit at harvest was not different from the control , and while the number of internal bruises per fruit was greater in fruit treated with 20 g ProGibb on 30 July than the control , no differences in the number of internal bruises was apparent among other treatments compared to the control after storage . Number of fruit dropped over time did not vary among treatments . When visual color of skin and flesh were rated on the fruit harvested on 31 July , there was no difference among treatments compared to the control in skin color and no difference among treatments for flesh color ; storage did not change this result . When fruit were evaluated by colorimeter , however , some differences among treatments were found for skin and flesh color for both harvests ; however , differences in chromacity , lightness and hue angle have not consistently related closely to maturity . Fruit from the second pick ( August 5 ) were not different with respect to firmness , fruit weight or visual skin or flesh color in â?? Andross â?? . ReTain did not improve fruit firmness in either â?? Andross â?? or â?? Ross â?? . GA and ReTain were ineffective in increasing firmness in â?? Ross â?? when compared to the control , although â?? Ross â?? fruit were firmer ( numerically ) when treated with 20 g ProGibb approximately 2.5 weeks before the single commercial harvest . Fruit size ( weight ) and fruit drop in â?? Ross â?? were unaffected by either GA or ReTain in 2003 . Problem and its significance : Several cling peach cultivars develop softening problems prior to harvest and in some orchards and seasons the problems can be pronounced . In field experiments conducted from 1993 to 1995 with â?? Loadel â?? cling peach we found that an application of gibberellin A ( GA ; or the commercial product ) could be sprayed 1 to 3 weeks prior to 3 harvest to improve fruit firmness ( Southwick and Fritts , 1995 ; Southwick and Glozer , 2000 ) . Our results with â?? Loadel â?? suggested an increase in fruit firmness of about 2 pounds ( Southwick , et . al . , 1995 ) . Other cling peach cultivars showed similar increases in fruit firmness with the appropriate GA spray application ( Southwick and Fritts , 1995 ) . Further research with GA to improve fruit firmness suggests a consistent response when applications are made 3 to 4 weeks prior to commercial harvest . The ethylene biosynthesis inhibitor ReTain ( Valent Biosciences Corp . , Libertyville , Illinois , USA ) has also been shown to improve firmness , delay harvest and reduce fruit drop in pome and stone fruit . Our work with apricot and the work of others with peach suggest that ReTain may help to improve the firmness of cling peach cultivars . The improvement in fruit firmness may help to reduce fruit bruising and may also be used as a harvest management tool to extend the normal harvest period for particular cultivars . In addition , improved firmness of fruit may help overcome some problems associated with mechanical harvest , especially for those cling peach cultivars less amenable to machine harvest such as â?? Andross â?? . The benefits from GA sprays may help to improve fruit quality from hand harvest as well . Our goal has been to demonstrate the utility of GA for harvest management and evaluate the potential of ReTain in cling peach production . Objectives : $ Determine whether GA sprays prior to harvest can consistently improve the firmness of â?? Andross â?? and â?? Ross â?? cling peach . $ Determine whether GA sprays prior to harvest may alter the harvest date of treated fruit . $ Determine the effects of preharvest ReTain spray treatment on the firmness and fruit drop of â?? Andross â?? cling peach . $ Determine the effects of preharvest GA sprays on return bloom . Return bloom with 2002 GA sprays Plans and Procedures , 2002 : The orchards used in 2002 were those used in the 2003 trials ( see below for description ) . The treatments used in 2002 are the following : Treatments ( applied at 100 gallons per acre volume ) Orchard A , â?? Andross â?? : Commercial harvests , and fruit sampling , was performed on 1 August and 9 August . 1 . Untreated control ® ProGibb ( 4 % gibberellic acid ; Valent Biosciences Corp . , Libertyville , IL ) + 0.1 % Regulaid as a surfactant 2 . 20 g a.i . per acre , applied ( 3 July ) 4 weeks before first harvest , 5 weeks before second harvest 3 . 20 g a.i . per acre , applied ( 10 July ) 3 weeks before first harvest , 4 weeks before second harvest 4 . 20 g a.i . per acre , applied ( 19 July ) 12 days before first harvest , 20 days before second harvest 5 . 32 g a.i . per acre , applied ( 3 July ) 4 weeks before first harvest , 5 weeks before second harvest 6 . 32 g a.i . per acre , applied ( 10 July ) 3 weeks before first harvest , 4 weeks before second harvest 7 . 32 g a.i . per acre , applied ( 19 July ) 12 days before first harvest , 20 days before second harvest ® 8 . ReTain ( aminoethoxy - butenoic acid hydrochloride , 15 % ; Valent Biosciences Corp . , Libertyville , IL ) , 50 g a.i . , applied approximately 7 days before first harvest , 15 days before second harvest ( label says 1 - 4 weeks before harvest ; in 2002 it was 8 days and 16 days , respectively ) Orchard B , â?? Ross â?? : Commercial harvest and fruit sampling was performed on August 9 . Treatments ( applied at 100 gallons per acre volume ) 1 . Untreated control ® ProGibb ( 4 % gibberellic acid ; Valent Biosciences Corp . , Libertyville , IL ) + 0.1 % Regulaid as a surfactant 2 . 20 g a.i . per acre , applied ( 10 July ) 4 weeks before harvest 3 . 20 g a.i . per acre , applied ( 19July ) 3 weeks before first harvest 4 . 20 g a.i . per acre , applied ( 31 July ) 8 days before first harvest 5 . 32 g a.i . per acre , applied ( 10 July ) 4 weeks before harvest ( 10 July ) 6 . 32 g a.i . per acre , applied ( 19July ) 3 weeks before first harvest 7 . 32 g a.i . per acre , applied ( 31 July ) 8 days before first harvest ® 8 . ReTain , 50 g a.i . , applied ( 24 July ) 2 weeks before harvest Return bloom was evaluated as counts of flower buds taken on two limbs per treated tree prior to full bloom on March 6 . Return bloom was calculated as number of flower buds per centimeter of shoot length . Data analysis : Statistical Analysis Systems software ( SAS Institute , Cary , NC ) was used to perform analysis of variance ( PROC GLM ) . Mean separation was by Duncanâ??s Multiple Range Test , 5 % level of significance . Results : No significant difference was found among treatments . Plans and Procedures , 2003 : Orchards A and B , commercial orchards of â?? Andross â?? and â?? Ross â?? cling peaches , respectively , were used as UCD trial orchards in the same immediate area north of Marysville , Yuba County , in the Sacramento Valley ; these same orchards were used for similar treatments in 2002 . All treatments applied at Orchards A and B were sprayed at a - 1 volume of 100 gallons per acre ( gpa ; 936 LÎ?ha ) , with the exception of 2 treatments with GA in â?? Ross â?? at 200 gpa , applied with a Stihl SR 400 mist blower ( Andreas Stihl , Waiblingen , Germany ) . In both orchard experiments , we used a complete random block design with 4 single tree replicates per treatment ( 4 blocks ) . Trees were guarded by unsprayed trees on all sides . Sprays were applied beginning approximately 7 to 8 am . Orchard A , â?? Andross â?? : Trees were planted at 18 ' x 16 ' spacing with 151 trees per acre . Trees were 5 years old ; the rootstock was â?? Lovell â?? . Irrigation was by micro sprinkler . Commercial harvests , and fruit sampling , was performed on 31 July and 5 August . Treatments ( applied at 100 gallons per acre [ gpa ] volume ) 1 . Untreated control ® ProGibb ( 4 % gibberellic acid ; Valent Biosciences Corp . , Libertyville , IL ) + 0.1 % Regulaid as a surfactant 3 2 . 20 g a.i . per acre , applied ( 23 July ) ~ 2 weeks before harvest ( anticipated harvest 15 Aug ) 3 . 20 g a.i . per acre , applied ( 30 July ) 4 . 20 g a.i . per acre , applied ( 6 Aug ) 5 . 32 g a.i . per acre , applied ( 23 July ) 6 . 32 g a.i . per acre , applied ( 30July ) 7 32 g a.i . per acre , applied ( 6 Aug ) ® 8 . ReTain ( aminoethoxy - butenoic acid hydrochloride , 15 % ; Valent Biosciences Corp . , Libertyville , IL ) , 50 g a.i . , applied 16 July Orchard B , â?? Ross â?? : Trees were planted at 21 ' x 21 ' spacing with 99 trees per acre . The orchard was a mixture of 4 year - and 15 year old - trees on â?? Lovell â?? rootstock . The orchard was flood - irrigated . Commercial harvest and fruit sampling was performed on August 8 at a single harvest , as was done by the grower . Treatments ( applied at 100 gallons per acre [ gpa ] volume or 200 gpa where indicated ) 1 . Untreated control ® ProGibb ( 4 % gibberellic acid ; Valent Biosciences Corp . , Libertyville , IL ) + 0.1 % Regulaid as a surfactant 2 . 20 g a.i . per acre , applied ( 23 July ) ~ 2.5 weeks before harvest ( anticipated harvest 15 Aug ) 3 . 20 g a.i . per acre , applied ( 30 July ) 4 . 20 g a.i . per acre , applied ( 6 Aug ) 5 . 20 g a.i . per acre , applied ( 6 Aug ) , 200 gpa 6 . 32 g a.i . per acre , applied ( 23 July ) 7 . 32 g a.i . per acre , applied ( 30July ) 8 . 32 g a.i . per acre , applied ( 6 Aug ) 9 . 32 g a.i . per acre , applied ( 6 Aug ) , 200 gpa ® 10 . ReTain , 50 g a.i . , applied ( 16 July ) Harvest , fruit sampling and evaluation : Orchard A : â?? Andross â?? We harvested on 31 July and 5 August beginning at approximately 6 : 30 am . At each harvest we harvested 20 fruits from each treated tree selecting at random from the bin that had been hand - picked by the commercial crew . Cumulative fruit drop was counted on 31 July , on each replicate treated tree . After weighing all fruit sampled at the 31 July harvest , fruit were divided into three groups of seven for evaluation and storage , such that fruit were evaluated immediately after harvest or stored at 32 Î?F for approximately 21 hours ( 26 hours post harvest ) or 5 days , then evaluated . Fruit from the second harvest were not stored . At each harvest , in addition to fruit mass ( weight ) and the number of undersized fruit in the 20 - fruit sample ( undersize diameter was less than 2 3 / 8 inches ) , fruit were evaluated for : $ Fruit firmness , determined with the skin off on both cheeks ( avoiding blushed areas ) by an Imada digital force gauge fitted with a conical tip and the ability to read up to 11 psi ( 5 kg ) of force . Readings from both cheeks were summed and averaged . $ Fruit color , visually assessed cheek skin and flesh colors compared to the California Department of Food 4 and Agricultureâ??s ( CDFA ) # 2 , green color chip ( L * = 75.0 , C * = 61.0 , H o = 85.9 ) to determine the percentage of green or yellow fruit . $ Fruit color ( cheek skin and flesh colors ) using a Minolta colorimeter ( Minolta Corp . , Ramsey , NJ ) that measured color parameters hue , lightness , chroma and color ( red / green ) balance . Blushed or bruised areas of the skin were avoided , as were bruised areas of the flesh . Flesh readings were taken with skin off . Orchard B : â?? Ross â?? : This orchard was harvested on a single date , 8 August , at which time 10 fruit were randomly selected from each treated tree , collecting all colors and sizes throughout the mid - canopy . These 10 fruit were used for fruit mass determination , percent undersized , visual skin and flesh color . Five fruit were sub - sampled for firmness and color evaluation by colorimeter as above . As no firmness differences were detected among treatments immediately after harvest , no storage was used in this trial . Data analysis : Statistical Analysis Systems software ( SAS Institute , Cary , NC ) was used to perform analysis of variance ( PROC GLM ) . Mean separation was by Duncanâ??s Multiple Range Test , 5 % level of significance . Results and discussion : Firmness of â?? Andross â?? peach was increased by GA sprays of 32 g / acre applied approximately 3 weeks before harvest on first pick fruit harvested and sampled on July 31 ( Table 1 ) . These fruit maintained improved firmness compared to the control for 21 hours after harvest , and were as firm as the control after 5 days . Fruit treated with 20 g / acre GA on 9 July were numerically firmer than the control fruit after harvest and throughout storage , although not statistically firmer . Fruit treated at 32 g / acre of GA on 16 July were equal to the control at harvest but grew less firm than the control with extended storage . Percentage of undersized fruit , number of fruit that dropped cumulatively , and weight per fruit were not different among treatments on 31 July ( Table 2 ) . The number of external bruises per fruit at harvest was not different from the control , and while the number of internal bruises per fruit was greater in fruit treated with 20 g ProGibb on 30 July than the control , no differences in the number of internal bruises was apparent among other treatments compared to the control for either storage period ( Table 2 ) . Number of fruit dropped over time did not vary among treatments ( Table 2 ) . When visual color of skin and flesh were rated on the fruit harvested on 31 July , there was no difference among treatments compared to the control in skin color and no difference among treatments for flesh color ( Table 3 ) . Thus , the percentage of green fruit at harvest was non significant . Similarly , no differences for either skin or flesh color when rated visually was found after storage for 21 hr ( Table 3 ) , nor after 5 days storage ( data not shown ) . When fruit were evaluated by colorimeter , however , some differences among treatments were found for skin color ( Table 3 ) and flesh color ( Table 4 ) . Similarly , differences among treated fruit in skin and flesh color measured at the second harvest exhibited some significance ( Table 5 ) . Nonetheless , these differences should be evaluated with caution as differences in chromacity , lightness and hue angle do not always relate closely to maturity , as per reports to the California Cling Peach Board by Crisosto et al . reflect : â?? . . . lightness ( L * ) , chromacity ( C ) , and hue angle ( H o ) color system . Since canning peaches do not darken excessively when ripe , like a plum for example , lightness is not an appropriate variable to express the relationship between color and maturity , where maturity is expressed in terms of fruit flesh firmness . Chromacity values are highly variable for a number of reasons . Therefore , hue angle which defines the actual hue in terms of red , green , yellow , blue , etc . as a 0 - 360 system is used for analysis of any color and maturity ( as firmness ) relationship . Hue angles of note for canning peaches are the ranges + 50 o ( orange ) through + 90 o ( yellow ) to + 135 o ( green ) , so as hue angle increases the fruit flesh color is greener . A significant , positive ( P value = 0.0001 ) relationship exists between skin hue angle values and flesh hue angle values as measured for â?? Andross â?? , â?? Carson â?? , and â?? Ross â?? fruit . 5 However , it is a poor linear relationship with R 2 = 0.36 ( â?? Andross â?? ) , R 2 = 0.23 ( â?? Carson â?? ) and R 2 = 0.24 ( â?? Ross â?? ) . Skin hue angle does not predict flesh hue angle well . â?? Fruit from the second pick ( August 5 ) were not different with respect to firmness ( data not shown ) , undersized fruit ( Table 5 ) , fruit weight or visual skin or flesh color ( data not shown ) . Fruit size ( % undersized ) , visual color of skin or flesh ( data not shown ) , weight ( Table 6 ) or preharvest drop ( Table 6 ) were not affected by the various treatments . GA sprays of 20 g / acre or 32 g / acre applied 4 weeks before harvest to â?? Ross â?? did not improve fruit firmness compared to the untreated check ( Table 6 ) . ReTain did not improve fruit firmness in either cultivar . There was no harvest delay noted as a result of ReTain treatment in this experiment . Pertinent literature : Southwick , S.M . and R . Fritts . 1995 . Commercial chemical thinning of stone fruit in California by gibberellins to reduce flowering . Acta Hort . 394 : 135 - 147 . Southwick , S.M . and K . Glozer . 2000 . Reducing flowering with gibberellins to increase fruit size in stone fruit trees : Applications and implications in fruit production . HortTechnology 10 : 744 - 751 . Southwick , S.M . , K.G . Weis , J.T . Yeager , and H . Zhou . 1995 . Controlling cropping in â?? Loadel â?? cling peach using gibberellin : Effects of flower density , fruit distribution , fruit firmness , fruit thinning , and yield . J . Amer . Soc . Hort . Sci . 120 : 1087 - 1095 . Table 1 . Effects of ProGibb and Retain on firmness in â?? Andross â?? cling peach at first harvest ( 31 July ) and after storage at 32 Î?F for 21 hours ( 26 hr postharvest , August 1 ) and 5 days ( August 5 ) . 31 July 1 August 5 August Treatment ( @ 100 gal / A ) lb N lb N lb N x Date applied Untreated control 3.9bc 17.3bc 3.7ab 16.5ab 3.8ab 17.0ab 9 July 4.5ab 19.9ab 4.3a 19.0a 4.1a 18.4a ProGibb 4 % 20 g 16 July 3.7c 16.6c 3.2ab 14.2ab 3.2bc 14.0bc a.i . / A , 0.1 % Regulaid 30 July 3.9bc 17.2bc 2.7b 12.1b 3.0c 13.4c 9 July 4.6a 20.7a 4.0a 18.0a 3.9ab 17.2ab ProGibb 4 % 32 g 16 July 4.4ab 19.6ab 3.2ab 14.3ab 2.9c 13.2c a.i . / A 30 July 3.8bc 17.0bc 3.4ab 15.3ab 3.7bc 16.6abc ReTain 50 g a.i . / A 16 July 4.1bc 18.0bc 3.2ab 14.2ab 3.2bc 14.0bc x Mean separation within columns by Duncanâ??s multiple range test , P = 0.05 . 6 84.2a color H harvest internal dropped flesh rating . tree 81ns 44.3c at and 63 88 88 71 76 91 56 per for # Fruit color inches . c visual skin and , skin and July ) 3 / 8 by July ) , for 42.9d evaluated August 2 0.50ns ( 31 fruit than b indices 0.54 0.57 0.57 0.25 0.43 0.54 0.50 harvest ( 31 per less 5 harvest color Colorimetric bruises diameter 3.7ab first a flesh first at # Internal August 0.21bc 0.14bc 0.11bc 0.22bc 0.39ab 0.32ab peach a colorimeter , at 0.07c 0.54a had peach fruit 69.3 1 cling L cling Undersized â?? Andross â?? color and bruises 1 â?? Andross â?? Aug 2.00 rating fruit Flesh 0.20abc 0.21abc 0.23abc 0.16abc significant . 0.09bc 0.34ab # External on 0.39a 0.07c in 5 ) . per visual color drop in ( August color fruit fruit Visual by 1.6 non Skin green evaluated cumulative days = 171.2ns grams ns of 156.2 162.5 173.8 156.2 156.2 166.2 146.2 fruit 5 0.05 ; percentage Green harvest and at color 41.7 per fruit 1 ) and = Weight August P % Skin size test , ounces 6.1ns and fruit 1 ) . 5.5 5.7 6.1 5.5 5.5 5.8 5.2 range postharvest , harvest color August bruising , Flesh 1.75 multiple 7 flesh at % Undersized postharvest , y color external and hr 1.7ns Duncanâ??s x 10.0 6.7 5.0 6.7 3.3 5.0 3.3 ( 26 skin 1.50ab Visual Skin hours on on hr Retain Retain by ( 26 21 applied July columns July July July July July July for Date hours applied and and Date 16 16 16 30 30 Î?F 9 9 21 ProGibb ProGibb 32 within for at a.i . / A storage Regulaid Î?F 100 100 separation of of control control a.i . / A 32 g g Effects Effects ( @ gal / A ) 20 32 at ( @ after gal / A ) Treatment storage Treatment g 4 % 4 % 0.1 % 50 Untreated Untreated bruising , 3 . 2 . Mean ProGibb ProGibb ReTain a.i . / A , Table Table after x 82.7ab 83.7ab 85.4a 86.2a 85.6a 84.7a 80.0b 45.4bc 45.6bc 47.8ab 46.7ab 46.6ab 48.8a 48.8a c c 44.0bcd 45.9a - d 45.5a - d 47.1ab 46.6ab 43.6cd 47.6a 3.4ab 2.6ab 4.1ab 5.7ab 4.6ab 2.2b 7.2a 69.8ns 69.8 69.7 68.4 70.2 68.8 70.3 differences . 1.96ns 1.86 1.89 1.92 1.89 1.89 1.89 significant 1.6ns 1.7 1.7 1.7 1.8 1.6 1.8 non = ns 0.05 ; 38.3ns 26.7 21.7 33.3 35.0 45.0 26.7 = P test , 2 . = range yellow 1.90ns 1.85 1.90 1.75 1.90 1.65 1.80 multiple 8 or maturity ) Duncanâ??s 1.55ab 1.50ab 1.60ab 1.75a 1.70a 1.70a 1.30b minimum by columns July July July July July July July ( below 16 16 16 30 30 9 9 within 1 = green separation a.i . / A g g 20 32 color : g 4 % 4 % 0.1 % 50 Regulaid Mean Visual ProGibb ProGibb ReTain a.i . / A , a.i . / A x y 5 84.3ab 83.3ab 84.3ab 80.3b 86.6a 86.7a 85.4a 86.5a and H postharvest ) 53.2bcd 52.6bcd 53.9abc 52.0cd 55.8ab 51.8cd 56.8a 50.3d August ) c hr ( 26 hours ( 5 52.8bcd 53.7abc storage 51.6cd 52.4cd 55.6ab 51.6cd 56.0a 49.7d 21 b for days Î?F 5 32 6.1ab After 5.5b 5.0b 3.3b 9.6a 3.3b 4.2b 3.3b at a storage differences . after 64.3ab 64.9ab 64.0ab 65.9ab 65.0ab 65.6ab 66.5a 63.0b L July ) significant ( 31 harvest 82.7ab 83.7ab 86.2a 85.4a 84.7a 85.6a 84.2a 80.0b H non first = ns August ) at 45.6bc 45.4bc 47.8ab 46.6ab 46.7ab 48.8a 48.8a 44.3c 0.05 ; peach c c c = ( 1 cling P storage test , 44.0bcd 45.9a - d 45.5a - d â?? Andross â?? 47.1ab 46.6ab 43.6cd 47.6a 42.9d range b hours multiple 9 in 21 color After 3.4ab 2.6ab 4.1ab 5.7ab 4.6ab 3.7ab 7.2a 2.2b a Duncanâ??s flesh on x 69.8n Retain 69.7 69.8 68.4 70.3 70.2 69.3 68.8 by L columns s and applied July July July July July July July Date ProGibb within 16 16 30 16 30 9 9 separation 100 of control a.i . / A g g Effects 20 32 ( @ gal / A ) g 4 % 4 % Treatment 0.1 % 50 Untreated Regulaid 4 . Mean ProGibb ProGibb ReTain a.i . / A , days . Table a.i . / A x % Undersized 3.6ns 14.3 14.3 21.4 10.7 10.7 7.1 7.1 83.3ab 84.3ab 85.4ab 84.3ab 86.6a 87.7a 86.5a 80.3b H 53.0abc 52.6bcd 53.2bcd 52.0cd 55.8ab 51.8cd 56.8a 50.3d c color 53.7abc 52.8bcd 51.6cd 52.4cd 51.6cd 55.6ab 56.0a 49.7d Flesh b 6.1ab 9.6a 3.3b 5.0b 3.3b 5.5b 4.2b 3.3b a August ) . ( 5 64.0ab 65.6ab 64.0ab 64.3ab 65.0ab 66.0ab differences . 66.5a 63.0b harvest L second significant 88.7ns at 89.3 91.2 89.0 88.8 87.1 87.1 90.2 H peach non cling = 46.8ns ns â?? Andross â?? 45.4 45.1 44.7 45.5 45.9 44.9 46.0 0.05 ; c = color P in test , 46.4ns size 44.9 44.6 44.1 45.0 45.2 44.4 45.2 Skin 10 range b fruit multiple and color - 0.28ab 0.90ab 1.08ab 1.21ab 0.45ab - 0.57b 2.42a 2.47a a Duncanâ??s flesh on 71.2n Retain by 70.6 71.0 69.4 69.4 71.4 71.2 70.6 L columns s and Applied July July July July July July July ProGibb within 30 16 16 30 16 9 9 separation of control g g Effects 20 32 ( @ gal / A ) Treatment g 4 % 4 % 0.1 % 50 Untreated Regulaid Mean 5 . ProGibb ProGibb 100 ReTain a.i . / A , Table a.i . / A a.i . / A x Table 6 . Effects of ProGibb and Retain on fruit quality in â?? Ross â?? cling peach at harvest ( 8 August ) . Applied Firmness Treatment ( @ 100 # Fruit dropped gal / A ) Fruit wt ( g ) cumulatively N lb Untreated control 15.6abc 3.5abc 192 37.8 23 July 18.5a 4.2a 17.8 37.6 ProGibb 4 % 20 g 30 July 15.6abc 3.5abc 184 43.2 a.i . / A , 0.1 % Regulaid 6 August 13.1bc 2.9bc 190 53 / 0 ProGibb 4 % 20 g a.i . / A 6 August 15.8abc 3.6abc 177 44 / 4 200 gpa 23 July 17.7ab 4.0ab 208 66.2 ProGibb 4 % 32 g a.i . / A 30 July 14.3c 3.2c 190 43.0 6 August 17.0ab 3.8ab 208 57.6 ProGibb 4 % 32 g a.i . / A 6 August 13.2c 3.0c 178 59.0 200 gpa ReTain 50 g a.i . / A 16 July 14.7bc 3.3bc 196ns 42.4ns x Mean separation within columns by Duncanâ??s multiple range test , P = 0.05 ; ns = non significant differences . 11