Southwick, Stephen :

Glozer Dr, Kitren

Hasey, Janine K

Hansen, Randy :

Labor / Cost Saving Technologies : Refining chemical thinning procedures for cling peach in 2003 ; testing mechanical thinning in 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 , surfactants , gibberellin , plant growth regulation , plant growth regulators , fruit thinning , machine thinning Summary : We conducted small scale efficacy trials with fish oils , soybean oils , organics and other chemicals in an orchard of â?? Loadel â?? / â?? Lovell â?? cling peach trees located in the Yuba City / Marysville area . A single trial comparing two seed oils were also conducted at UCDâ??s Wolfskill Experimental Orchard on â?? Oâ??Henry â?? peach trees . The orchard selected in 2003 was fairly vigorous and typically highly productive . In 2002 in a less vigorous and productive â?? Loadel â?? orchard , 2 % Entry reduced fruit set by 80 % ( 8.3 % set ) and 3 % Entry reduced fruit set by 63 % ( 15.6 % set ) ; these were statistically equivalent . Also in 2002 , 3 % Entry applications made at 12 : 00 noon significantly reduced fruit set while applications made at 10 : 15 a.m . or 3 : 00 p.m . were not as effective . Drying times were significantly shorter in 2003 , although ambient temperature , relative humidity and presence of wind were not very different from those in 2002 . Based on results from 2002 and 2003 , we suggest that orchards which tend to over - produce may benefit from an Entry application of 2 - 3 % within a day or two prior to full bloom . Orchards which tend to be less productive could be effectively thinned with 2 % Entry at 40 - 80 % of full bloom . Applications should be made when a longer drying time is anticipated , i.e . when temperatures are 60Î?F or cooler , relative humidity is at least 50 % , and there is little wind . Additional experiments were conducted in 2003 with the surfactant Entry to test the effects of added ammonium thiosulfate ( ATS ) and urea . We found that 2 % Entry plus ATS was more effective than either Entry or ATS alone . 2 % Entry + 4 % ammonium thiosulfate reduced fruit set 70.5 % compared to the control . This treatment was phytotoxic to floral and vegetative bud death , as well as resulting in shoot dieback , as was also seen in 2002 . Similar phytotoxicity was seen in the 2003 treatment of ATS alone and the Entry + 15 % urea treatment , although to a lesser degree . We believe that a lower concentration of Entry or ATS could help reduce phytotoxicity while achieving effective thinning . A single organic treatment , that of 4 % fish oil + 5 % lime sulfur applied on March 8 , reduced fruit set 19 % compared to the control . No other organic treatment resulted in a significant reduction in fruit set , although an acetic acid treatment ( 1 qt / 100 gal Dyne - Amic spreader ( 0.25 % ) + 1 qt / 100 gal Tomahawk ( citric acid , acetic acid buffer ) + 10 % v / v of glacial acetic acid ) did reduce set numerically compared to the control . Seed oils did not reduce fruit set in either of two trials in which stage of bloom development ( / bud stage ) was considered , whether treatments were compared within bud stages ( data not shown ) or across bud stages . We conducted machine thinning trials in collaboration with Mr . Erik Nielsen of Nielsen Enterprises . The orchard used was included in the green drop program and so the grower was willing to experiment with thinning by machine , but was not farming the block seriously after the thinning operation was performed . However , it was deemed to be a good location to experiment in a preliminary way . We machine - thinned fruit during the early pit - hardening period and made adjustments in the shaking patterns and other machine variables to remove an appropriate number of fruit per tree to a desired level . Although machine - thinning did not always uniformly thin fruit throughout the canopy ( for example , heavier thinning in the top of the tree ) , it was clear that fruit could be removed quickly and with good success . Additional work should be conducted in 2004 wherein controlled trials could be performed with interested cling peach grower cooperators . Problem and its significance : Thinning peaches is one of the highest costs for cling peach producers and is generally required to ensure adequate fruit size . Over the last several years we have been working to develop chemical thinning programs in an effort to reduce the cost of hand thinning or improve the labor efficiency of hand thinning . Since we started this work two products have been made available to the cling peach industry for chemical thinning . A surfactant , Entry , can be used at bloom to reduce fruit set and reduce the number of fruit needed to be thinned by hand . Another product , gibberellin A can be sprayed in the growing season usually late June to mid - July to reduce the number of 3 , flowers in the following season leading to less fruit and a reduction in the need to thin . These chemical thinners do not allow the grower to visualize the fruit on the tree and then remove a portion of them . The sprays must be applied prior to final fruit set . Moreover , there is variation in the thinning response when using these chemical thinners , which is not unusual when using any chemical thinner in a fruit production program . Our goal has been to identify chemical thinning agents , determine their potential , help to ensure they will be available to the cling peach industry for use and work to develop methods so their use can be effective and help to sustain the California Cling Peach industry . In 2002 we investigated the effects of varying concentration of Entry at different application timings during a single day , as well as the effects of applying Entry with various fertilizers . Specifically , we applied Entry at a 2 or 3 % v / v concentration in 100 gallons per acre when 40 to 60 % of the flowers were in late popcorn or full bloom , and found that in each case Entry reduced fruit set by 50 % or more compared with the untreated in â?? Loadel â?? cling peach . The addition of 10 % w / v urea , 5 % v / v calcium ammonium nitrate or 2.5 % v / v ammonium thiosulphate to the Entry sprays did not improve the thinning action of the Entry sprays . The thinning effect of the Entry spray was found to vary depending upon the time of the day in which it was applied . When Entry was sprayed at 3 % in 100 gallons per acre at 10 : 00 am , 12 : 00 noon and 3 : 00 pm the reduction in fruit set was most effective at 12 : 00 noon compared with the other two spray timings . Temperatures at 12 : 00 noon were about 68 Î?F , relative humidity was 50 % and it took about 10 minutes for the spray solution to dry . In addition , we found variation in the thinning response to Entry sprays within treatments based upon the number of late popcorn to full bloom flowers . Flowers in that stage were most sensitive to fruit set reduction by Entry spray . Moreover , as the number of flowers on the treated trees were in the petal fall stage , the reduction in fruit set from the Entry spray was less . Therefore , we suggested that Entry sprays should be made when temperatures are from 65 to 75 Î?F and from 40 to 60 % of the flowers should be in late popcorn to full bloom stage when sprays are applied to maximize the effects . These results required validation in 2003 . Mechanical thinning of cling peaches has been tested to a limited extent with cling peaches . Previous experience has suggested that the thinning is not well balanced within the tree , large fruit might be lost at the expense of small fruit , trunk damage may occur . Growers have not accepted machine thinning . However , new considerations have arisen since those tests were conducted and opinions formulated . The cost of thinning continues to rise and the ability to find labor to hand thin may become increasingly difficult . At the same time machine thinning has become more sophisticated . The prune industry in California widely depends upon machine thinning and even fresh market plum ; pluot and apricot growers have had success with machine thinning , especially when crops are very high . Computer programs are available that help determine an appropriate shaking pattern for the tree and crop load to remove an adequate number of fruit . Fruit damage is minimal . Machine thinning could be used in conjunction with chemical and / or hand thinning . In 2003 we began working with a commercial machine operator to demonstrate the utility of machine thinning in cling peaches . Objectives : $ Conduct small - scale efficacy chemical thinning trials with novel chemicals or combinations of chemicals . $ Conduct experiments to understand more about what conditions or factors contribute the variation in the response to chemical thinning agents . $ Initiate mechanical thinning trials to determine the utility of existing machines to thin peaches toward reducing the need for hand thinning Plans and Procedures : Chemical thinning trials - 1 Methodology common to all thinning trials included application of chemicals at a volume of 100 ( 936 LÎ?ha ) gallons per acre applied with a Stihl SR 400 mist blower ( Andreas Stihl , Waiblingen , Germany ) , with the exception of the two trials that tested two seed oils applied at different concentrations and bud stages , which were applied with hand sprayers to wetness . In each experiment we used a complete random block design within a single â?? Loadel â?? / â?? Lovell â?? orchard in the Marysville area ( oils were also applied in UCDâ??s Wolfskill Experimental Orchard ) . Three single - tree replicates were used for each treatment in each trial that utilized a mist blower ; in the Entry trials 2 shoots per tree were evaluated . Three shoots per treated tree were evaluated for fruit set in the trial with organics . Trees were guarded by unsprayed trees on all sides . Prior to treatment , shoots were chosen on each treated tree that were representative of the bloom overall on the given tree ; shoots for trials in Marysville were chosen on March 5 when trees were at approximately 10 - 20 % of full bloom . Shoots were spaced more or less evenly around the tree periphery . Prior to treatment , the number of flower buds was counted on each shoot for determination of percentage fruit set . Full bloom was approximately March 12 . On April 30 , prior to commercial hand thinning we counted the number of fruit ( excluding â?? button â?? fruit ) for fruit set counts . We also evaluated for phytotoxicity . I . Entry plus fertilizer trial : Treatments were applied on March 6 . 1 . Untreated control 2 . 2 % Entry 3 . 2 % Entry + ATS ( 4 % ) 4 . ATS 4 % 5 . 2 % Entry + 15 % Urea 6 . 15 % Urea 7 . 2 % Entry + 10 % CAN17 w / v 8 . 10 % CAN17 II . Entry Time Trial : A thinning trial testing the effects of application timing ( time of day ) , ambient temperature , relative humidity and drying time using 2 % Entry . Entry was applied on March 6 . Treatments included : 1 . Untreated control 2 . 2 % Entry ( Time of Day ) â?? 8 : 30AM , 10 : 30AM , 2 : 15PM III . Chemical thinning with organics : applied on either March 6 or March 8 A . March 6 1 . untreated 2 . 2.5 % lime sulfur w / v 3 . 5 % lime sulfur 4 . 10 % acetic acid v / v B . March 8 1 . Untreated 2 . 2 % fish oil ( Crockerâ??s Fish Oil , Quincy , WA 3 . 4 % fish oil 4 . 2 % fish oil + 5 % lime sulfur 5 . 4 % fish oil + lime sulfur 6 . 5 % NC - 99 a calcium / magnesium brine solution ( Genesis Agri Products , Inc . , Union Gap , WA ) 7 . 10 % NC - 99 In the trials with two seed oils , the trial at UCDâ??s Wolfskill Experimental Orchard ( WEO ) involved oils ( Dyne - Amic and RNA MO ) that were applied on two dates . Experimental plots were laid out as complete random block designs with three single - shoot replicates per treatment within a single row of â?? Oâ??Henry â?? trees . Shoots selected for treatment had a range of bud break stages at the time of treatment , although most buds were in a single stage of development on each treatment date . On February 21 , all buds on a treated shoot that were not in â?? white tip â?? stage with tips of petals visible , were removed ( buds less advanced and buds more advanced ) ; on February 28 , all buds on treated shoots that were not at early balloon stage were removed . Trees with treated limbs had no more than four shoot replicates per tree ; shoots were 1 to 3 meters from the ground surface and well - spaced around the canopy . The trial located in Marysville was also laid out as complete random block designs with three single - shoot replicates per treatment , per bud stage , within two adjacent rows , however all treatments were applied on March 6 . Shoots were treated as above in order to represent a single bud stage per shoot . Statistical Analysis Systems software ( SAS Institute , Cary , NC ) was used to perform analysis of variance ( PROC GLM ) . Treatments were compared within a given bud stage and across bud stages in both trials . Mean separation was by Duncanâ??s Multiple Range Test , 5 % level of significance . IV . Chemical thinning with seed oils : A . Marysville trials - - applied March 5 ; we identified various flower development stages at the time of spraying and noted the response as a function of flower stage . All sprays were by hand sprayer to wetness . 1 . Untreated 2 . 1 % Dyne - Amic blend of methylated vegetable oils with organosilicone - based surfactants ( Helena Chemical ) 3 . 5 % Dyne - Amic 4 . 1 % RNA MO ( methylated soybean oil ; RNA Corp . ) 5 . 5 % vegetable oil concentrate Bud stages represented : 1 . white tip 2 . balloon ( popcorn advanced ) - anthers protruding 3 . anthesis - petal fall B . WEO trials â?? applied February 21 and 28 at bud stages pink bud and early balloon , respectively 1 . Untreated 2 . 1 % Dyne - Amic , applied Feb 21 3 . 5 % Dyne - Amic , applied Feb 21 4 . 1 % Dyne - Amic , applied Feb 28 5 . 5 % Dyne - Amic , applied Feb 28 Results and Discussion : Chemical thinning trials Thinning trials of Entry in 2002 demonstrated the thinning efficacy of 2 % and 3 % Entry for â?? Loadel â?? / â?? Lovell â?? peach when applied shortly before full bloom ( Table 1 ) . In 2002 , 2 % Entry reduced fruit set by 80 % ( 8.3 % set ) and 3 % Entry reduced fruit set by 63 % ( 15.6 % set ) ; these were statistically equivalent . In 2002 , the Entry spray of 2 % was slightly more effective than the Entry spray at 3 % . When viewing the percentage of flowers in various stages it was found that more flowers were in the petal fall stage where the Entry 3 % treatment was applied . Our previous work with Entry had shown that spraying at petal fall is less effective for reducing fruit set when compared to fully open or flowers in the popcorn stages . The higher number of flowers in the petal fall stage suggests a reason why the 2 % Entry spray was slightly more effective than the 3 % concentration and is an example of how flower bud stage can contribute to the variation in response when Entry is applied during bloom . Trials planned in 2003 were based on 2002 results , in which 2 and 3 % Entry gave statistically equivalent results and , in this case , overthinned . We chose to use 2 % Entry and apply at an earlier bloom stage ( 10 - 20 % of full bloom ) , so as to reduce the risk of overthinning , as well as testing the efficacy on earlier bloom stages . The orchard used in 2003 proved to be more productive than that used in 2002 , no buds were fully open at the time of spraying , and the thinning response was not pronounced ( Table 2 ) . Bloom sprays of 2 % Entry at different timing / temperature / relative humidity and drying time combinations did not reduce fruit set in â?? Loadel â?? cling peach compared to the untreated control ; there were no significant differences among the treatments ( Table 2 ) . In 2002 , we observed that there were no significant differences in the amount of buds in various stages for each treatment ( Table 1 ) , but that variation was substantial . We suggested that those results may indicate that bloom stages present at the time of spray may contribute to the thinning response . For example , there were treatments applied where 60 % of the treated flowers were in the late popcorn to full bloom stage while other treatments had as few as 39 % of the flowers in that stage which is most susceptible to Entry sprays . In 2002 , 3 % Entry applications made at 12 : 00 noon significantly reduced fruit set while applications made at 10 : 15 a.m . or 3 : 00 p.m . were not as effective ( Table 3 ) . In 2003 we did not find any significant effect of temperature , relative humidity or drying time on the thinning activity of 2 % Entry ( Table 2 ) . Drying times were significantly shorter in 2003 , although ambient temperature , relative humidity and presence of wind were not very different from those in 2002 . Based on results from 2002 and 2003 , we suggest that orchards which tend to over - produce may benefit from an Entry application of 2 - 3 % within a day or two prior to full bloom . Orchards which tend to be less productive could be effectively thinned with 2 % Entry at 20 - 50 % of full bloom . Applications should be made when a longer drying time is anticipated , i.e . when temperatures are 60Î?F or cooler , relative humidity is at least 50 % , and there is little wind . In 2002 , no Entry / fertilizer combination ( urea 10 % w / v ; calcium ammonium nitrate 5 % v / v , or ammonium thiosulphate 2.5 % v / v ) decreased fruit set when compared to applications of Entry alone ( Table 4 ) . Ammonium thiosulphate ( ATS ) caused some phytotoxicity to small shoots in the form of floral and vegetative bud death , as well as shoot dieback . In the 2003 trial of Entry in combination with fertilizers , ( urea 15 % w / v ; calcium ammonium nitrate 10 % v / v , or ammonium thiosulphate 4 % v / v ) , a single treatment was statistically different than the untreated control ( Table 5 ) . 2 % Entry + 4 % ammonium thiosulfate reduced fruit set 70.5 % compared to the control . This treatment showed the same phytotoxic symptoms as seen in 2002 . Similar phytotoxicity was seen in the treatment of ATS alone and the Entry + 15 % urea treatment , although neither of these showed the extent of shoot death found in the Entry + ATS treatment , nor was fruit set in these significantly different than that of the control . It may be possible to reduce fruit set without shoot dieback with 2 % Entry in combination with ATS at a concentration below 2 % . . A single organic treatment , that of 4 % fish oil + 5 % lime sulfur applied on March 8 , reduced fruit set 19 % compared to the control ( Table 6 ) . No other organic treatment resulted in a significant reduction in fruit set , although the March 6 acetic acid treatment ( 1 qt / 100 gal Dyne - Amic spreader ( 0.25 % ) + 1 qt / 100 gal Tomahawk ( citric acid , acetic acid buffer ) + 10 % v / v of glacial acetic acid ) did reduce set numerically compared to the control . When treatments were compared across treatment dates ( statistics not shown ) , no treatment was significantly different from the control . Further work using fish oil + lime sulfur and an acetic acid mixture is warranted . Seed oils did not reduce fruit set in either trial ( Tables 7 , 8 ) , whether treatments were compared within bud stages ( data not shown ) or across bud stages . 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 . Plans and Procedures : Mechanical thinning trial An orchard in the Live Oak area was chosen as the grower was in the green drop program . We machine - thinned fruit during the early pit - hardening period on May 30 . Several consecutive rows of trees were chosen and four trees in each row were used for shake - thinning at different timings . The timing intervals for shake treatments were 5 / 8 sec , 3 / 4 sec , 1 sec and 1 1 / 8 sec . After shaking , all fruit from one half of the ground surface below each tree were counted . Number of fruit per pound was obtained for an estimate of the total weight of fruit removed . In addition to timing of shaking interval , the operator made adjustments in the shaking patterns and other machine variables to attempt to remove an appropriate number of fruit per tree to a desired level . Results and Discussion : Mechanical thinning trials Results were variable in that machine - thinning did not always uniformly thin fruit throughout the canopy ( for example , heavier thinning in the top of the tree ) , however , it was clear that fruit could be removed quickly and with good success . Additional work should be conducted in 2004 . fall Full a a b Petal 35.2 34.6 16.5 pm . 12 approximately to popcorn n.s . bloom 47.4 49.4 full 39 arcsine at Late set was ns 2002 x 69.1 70.0 65.5 Fruit 75.7 2003 . day by stage 11 , transformed the early 6 , March bud of March popcorn n.s . to temperature of tip on Percentage 17.4 12.8 19.1 differences . on White acre Percentages time min min times min per Drying 10 - 15 8 - 12 High 5 various gallons bud significant mistblower . significant . ab scales Expanded b a at 100 3.7 6.3 10.9 applied at humidity non applied non by Entry , = n.s . applied 68 50 42 = Relative Ttreatments bud ns 0.05 ; 0.05 , n.s . 2 % Closed acre , by time . = 2.7 0.9 4.1 = peach P per test , P 2002 . test , that Temperature gallons cling range at Range 50 64 70 peach , length cm 38 % â?? Loadel â?? multiple 100 per shown . Multiple was bc cling a c # Fruit shoot approximately 0.04 0.11 0.02 humidity in Duncanâ??s â?? Loadel â?? are set Duncanâ??s am pm am Time means fruit 10 : 30 8 : 30 2 : 15 relative in set at by on actual Y set v / v , by % Fruit Effect columns b b a fruit 15.6 8.3 41.8 pm ; separation 2 % , transformation ; y Treatment on 2 . 3 : 30 Entry untreated was within Table Entry at 12 . Entry Mean 2 % 72Î?F of separation control March Treatment Effects y x was Untreated Entry Entry 1 . Mean Table bloom 2 % 3 % X n.s . fall 35.2 34.6 35.1 36.1 Petal were time to drying popcorn bloom n.s . 39.6 47.9 47.4 43.2 full and Late stage temperature bud popcorn to n.s . of tip ( RH ) , Percentage White 12 . 17.4 12.8 12.8 18.5 early March humidity differences . was scales Expanded n.s . relative bloom 2.7 6.3 3.7 0.3 bud significant Full 2002 ; 2002 . bud n.s . peach , Closed non 0.5 0.9 2.7 0.0 11 , blower . = cling March n.s . 0.05 ; â?? Loadel â?? length cm n.s . mist on per acre = 0.06 0.04 0.11 0.11 by # Fruit shoot P test , in per applied set gallons range fruit acre , set X ab ab b a on multiple % Fruit 100 26.7 15.6 41.8 32.9 times per approximately gallons various Duncanâ??s % RH , 30 time 100 8.5 10 at 52 , ( min . ) 50 , Temp.Î?F , 32 , applied by approximately drying at 60 - 64 , 68 , columns 70 , applied y Entry treatments within application of at pm pm am 3 % v / v , Time 10 : 15 12 : 00 3 : 00 of separation 3 % , Effects All was evaluated . . Treatment Untreated Entry 3 . Mean control Entry Table 3 % X y Z Phytotoxicity at x x 2002 11 , March n.s . fall 23.2 16.5 19.3 34.6 37.8 30.7 35.2 26.3 26.9 Petal on acre per popcorn bloom n.s . gallons 56.1 60.0 49.4 39.0 48.2 43.6 47.4 44.2 58.4 full stage Late 100 to bud at popcorn differences . applied to each n.s . tip 11.1 19.1 11.4 14.1 13.9 17.4 22.3 12.8 dieback . White in 8.2 treatments early Percentage significant shoot scales Expanded n.s . All small 10.9 7.8 7.1 5.9 5.2 6.3 3.8 3.7 2002 . bud non 5 and = peach , n.s . leaves bud n.s . 0.05 ; Closed cling 1.8 4.1 2.2 1.1 2.1 0.9 0.9 2.7 1.5 few = â?? Loadel â?? buds , P test , floral length cm range bc bc bc ab per in c c c c a 0.04 0.02 0.03 0.04 0.02 0.04 0.09 0.02 0.11 set # Fruit shoot and multiple fruit vegetative 12 . on Duncanâ??s fertilizers set Y March bc bc c c b c c c a % Fruit 9.6 8.3 17.5 27.4 8.1 20.0 15.6 11.9 41.8 dead was by include various columns bloom thiosulfate Entry Entry Entry Entry Entry Entry Entry Entry to Full & found Entry within 2 % 2 % 3 % 3 % 3 % 2 % 2 % 3 % pm . Treatment was ammonium of separation control 12 Effects v / v v / v w / v Phytotoxicity approximately â?? Control â?? X CAN17 urea ATS Untreated 4 . = Mean ATS Table 10 % 2.5 % 5 % X Z Y Table 5 . Effect on fruit set in â?? Loadel â?? cling peach by 2 % Entry with various fertilizers , applied on March 6 , 2003 . y Treatment Fruit set x Untreated 65.5 a 2 % Entry 68.6 a Entry + 4 % ammonium thiosulfate ( ATS ) 19.3 b 4 % ATS 50.8 ab Entry + 15 % Urea 51.8 ab 15 % Urea 49.7 ab Entry + 10 % CAN17 47.2 ab 10 % CAN17 33.2 ab x Mean separation by Duncanâ??s Multiple Range test , P = 0.05 . Percentages transformed by arcsine transformation ; actual means are shown . y All treatments applied at approximately 100 gallons per acre , by mistblower . Table 6 . Effect on fruit set in â?? Loadel â?? cling peach by various organics in 2003 . z Treatment % Fruit set March 6 applications y untreated 65.5 2.5 % lime sulfur w / v 67.3 5 % lime sulfur 70.5 10 % acetic acid v / v 56.3 ns March 8 applications Untreated 67.1 ab 2 % fish oil 78.5 a 4 % fish oil 76.7 ab 2 % fish oil + 5 % lime sulfur 61.8 ab 4 % fish oil + lime sulfur 54.4 b 5 % NC - 99 76.8 ab 10 % NC - 99 61.4 ab x acetic acid mixture = 1 qt / 100 gal Dyne - Amic spreader ( 0.25 % ) + 1 qt / 100 gal Tomahawk ( citric acid , acetic acid buffer ) + 10 % v / v of glacial acetic acid y Mean separation by Duncanâ??s Multiple Range test , P = 0.05 , ns = non significant . Percentages transformed by arcsine transformation ; actual means are shown . z All treatments applied at approximately 100 gallons per acre , by mistblower . Table 7 . Effect on fruit set in â?? Loadel â?? cling peach by seed oils , applied on March 6 , 2003 . y Treatment % Fruit set x Untreated 70.7 1 % Dyne - Amic 75.0 5 % Dyne - Amic 63.6 1 % vegetable oil concentrate 67.6 5 % vegetable oil concentrate 70.6 ns x Mean separation within an application date by Duncanâ??s Multiple Range test , P = 0.05 , ns = non significant . Percentages transformed by arcsine transformation ; actual means are shown . y All treatments made by hand sprayer to wetness . Table 8 . Effect on fruit set in â?? Oâ??Henry â?? cling peach by seed oils , 2003 . z y Treatment Application timing % Fruit set x Untreated 63.8 1 % Dyne - Amic Feb 21 67.2 1 % Dyne - Amic Feb 28 59.0 5 % Dyne - Amic Feb 21 60.7 5 % Dyne - Amic Feb 28 65.3 ns x Mean separation within an application date by Duncanâ??s Multiple Range test , P = 0.05 , ns = non significant . Percentages transformed by arcsine transformation ; actual means are shown . y Application timings made Feb 21 and 28 were at pink bud and early balloon stages , respectively . z All treatments made by hand sprayer to wetness .