i. l. r 5. tr as .. mry @1969 and 1970, Fruitone CPA was sprayed on peach ' to determine its effectiveness for thinning peaches. ntration rates were 0, 150, and 300 parts per million ). Fruitone CPA caused fruit thinning, but the results E erratic. Factors other than concentration rates appar- g1 influence the effectiveness of this chemical as a peach ner. ‘a - duction . g to citrus, peaches are the most important Texas fruit - Because of several problems, however, Texas pro- i7 less than one-half of the peaches consumed in the V, A major production problem is setting too much fruit v f: ee. Many chemical compounds have been evaluated inomical peach thinning agents (2, 3, 4), but none have If consistently adequate. One of the more recent materials d for trial is Fruitone CPA [2-(3-chlorophenoxy)-pro- mide] [2-(3-chlorophenoxy)-proprionic acid] 1. To the quality of the peaches and to find an alternative nd thinning of peach fruit, the effectiveness of CPA as gner was evaluated under conditions in Texas. ‘ te professor, The Texas Agricultural Experiment Station f tment of Soil and Crop Sciences) and (formerly) horticulturist, exas Agricultural Extension Service, (presently) horticultural ion specialist, Tifton, Georgia. c! actured by Amchem Products, Inc. i__n of a trademark or proprietary product does not constitute .ntee or warranty of the product by The Texas Agricultural = ent Station or the Texas Agricultural Extension Service l not imply its approval to the exclusion of other products "fai may be suitable. ‘ ‘I FlDS: peaches/fruit thinning/Texas. THE TEXAS AGRICULTURAL EXPERIMENT STATlON / J. E. Miller, Director Texas A&M University System / College Station, Texas B-1 168 November 1976 Effects of Fruitone CPA on Thinning Peaches in Texas By H. H. Bowen and A. A. Powell* Materials and Methods In 1969, Fruitone CPA was applied to peach varieties Redskin, Ranger, and Redglobe at rates of 0, 150, and 300 parts per million (ppm). Trees were 4, 7, and 8 years old, respectively, and in good horticultural condition. Plots consisted of 5 trees each and were replicated 3 times, in a randomized completed block design. Just prior to treatment and before any natural fruit drop, approximately 100 fruits were harvested at random from each variety to obtain embryo length measurements. These measurements determined how close embryo length was to 7 to 10 millimeters (mm), which was considered optimum for application of the thinner. CPA was applied with a hand gun from a hydraulic sprayer having return flow jet agitation at about 100 pounds per square inch (psi) pressure. Trees were sprayed to runoff. For evaluation of the treatments 150 fruits were initially identified and counted on three sectors of each tree. After treatment and after all fruit drop had occurred, the remaining fruit was counted. Then these fruits were hand thinned to a standard 6-inch spacing, and the number of fruits removed was recorded. Treatments were repeated in 1970 on the same Redskin and Ranger plots. Selected Redglobe trees were treated for observational purposes only. Results When CPA was applied, embryo lengths for varieties Red- skin, Redglobe, and Ranger were 8.0, 6.6, and 5.2 mm, respectively. Under some conditions Fruitone CPA effec- tively thinned peach fruit, but the results were highly var- iable. A concentration of 150 ppm did not remove adequate numbers of fruit (Table 1). 1 same letter are statistically different at the 5 percent level of probability. TABLE 1. AMOUNT OF PEACH FRUIT HAND THlNNED FROM TREES TO ADJUST FRUIT LOAD AFTER NATURAL DROPS - AND CHEMICAL THINNING WITH FRUITONE CPA Fruitone CPA 0 ppm (control) i 150 ppm 300 ppm Variety Lbs fruit/tree Percentage of Control 12552 Redskin 13.oa‘ 64b 17c Redglobe i 10.8a 89ab 44b Ranger 2.62 46 0 ' 19.19. Redskin 18.8a 64a 43a Ranger 20.2a 98a 43a All comparisons among treatments by variety not followed by the 2 Nonreplicated. In 1969, when the fruit crop was of moderate density, the 300 ppm concentration was satisfactory on Redskin trees, but in 1970 when the crop was heavy, thinning was inadequate. In 1969, this thinning treatment removed all fruit from Ranger trees, which were carrying a very light crop. ln 1970, results were similar to those with Redskin. Redglobe variety was the most difficult to thin, the results being unsatisfactory. Some trees were adequately thinned, while some showed little effect of the thinner. Light to moderate leaf abscission occurred on trees of all varieties receiving the 300-ppm rate. After hand thinning the fruit on all trees to the standard 6-inch spacing, the percent fruit remaining per counted region declined with increase in chemical thinning rate on all varieties except Redglobe. The results were not statisti- cally significant in all cases (Table 2). Throughout individual tree canopy, this relationship probably can be attributed to nonuniform thinning by Fruitone CPA. Such heavier thinning at the higher chemical rate would not necessarily be unde- sirable,since experience and research often have shown inad- equate fruit removal by hand thinning alone. Discussion and Conclusions Fruitone CPA can induce adequate fruit thinning; however, several factors such as varietal response, physiological stage of fruit development, concentration of thinner, weather All programs and information of The Texas Agricultural Ex TABLE 2. PERCENTAGE OF FRUIT REMAINING AFT DROPS AND HAND THINNING (BASED ON 150 FRUIT g Variety Year If ppm O 150 Average number of fruit - a _ Redskin 1969 1513a‘ 14.6a A 1970 26.3a 21 .7b Ranger 19692 13.5 8.2 1970 31 .0a 23.5a Redglobe 1969 11.0a 10.7a 1 All means in the same row followed by the same letter = tistically different at the 5-percent level of probability. Nonreplicated. conditions, and physiological state of the tree appar interact to affect the extent of fruit abscission (1 l. observations during this study, variable physiological a: of trees appeared to be the most serious cause of vari in tree to tree thinning. This variability is apparently-i. ated with soil conditions and root problems that wo be practical to control. Since extent of fruit abscissi, closely related to tree physiology, discovery of a sati, I chemical thinner may be difficult. ‘i’ References 1. Bowen, H. H. 1968. Efficiency of two chemical thinners Redskin peaches as affected by wind, temperature and -- I hl-ImidifY- Texas Agriculture Experiment Station PR-2 ' 2. Clark, R. K. 1968. Summary of Fruitone CPA perfor several states. Memeograph. 3. Martin, G. C. 1975. Peach thinning in California. ln" E edited by N. F. Childers. Horticultural PublicationfNew N. J. p. 288. i‘ 4. Thompson, A. H. 1975. Chemical thinning of peaches. In Peach," edited by N. F. Childers. Horticultural Publicati Brunswick, N. J. p. 287. “ > Acknowledgments A»; Appreciation is extended to Mr. E. E. Lightsey for the“ his orchard and to Amchem Products, lnc. for supplyi CPA for these studies. Station are available to everyone without regard to race, color 0' sex, age, or national origin. ._ 4