34 CIRCULAR 867, U. S. DEPARTMENT OF AGRICULTURE 



4.5 buds per foot of growth, while those chemically thinned at bloom 

 time had formed 12.1 buds per foot of growth. Although the average 

 tree yield of the dinitro-thinned trees was less in 1945 than in 1944, 

 the trees that were hand-thinned in 1944 yielded only one-third as 

 much fruit in 1945 as those trees that were chemically thinned in 

 1944 and again in 1945. 



Edgerton (10) has shown that the fruit buds on dormant peach 

 trees chemically thinned the previous spring show more resistance to 

 winterkilling than buds on trees not thinned or hand-trimmed during 



Table 10. — A comparison of dinitro sprays at olooming time and of 

 growth-regulating thinning sprays 1 month later for reducing 

 the set of peaches, 1950 





Treatment 



Concen- 

 tration 

 per 100 

 gallons 



Date 



applied 



Blossoms setting 

 fruit- 



Average 

 weight 





June 8 



July 10 



per fruit 

 July 10 





[Check 



DNNo.289. 



NAA 1 



do 



( do..... 



Check 



sDNNo.l... 



NAA 1 



Check 



DN No. 289 _ 



NAA* 



do 



Quantity 









Percent 



69 



69" 

 70 

 75 

 69 



--- 



55 



57" 

 50 



Percent 



23 



19 



14 



9 



2 



45 



32 



20 



30 



20 



10 



7 



Grams 



27 



Golden Jubilee. _ 



.opt 



15 p. p. m_ _ 



20 p. p. m_ _ 



30 p. p. m_ . 







May 6 



June 8 



___do___ 



...do... 



30 

 31 

 34 



27 



Halehaven 



.51b 



30 p. p. m. . 

 



May 6 

 June 8 



34 

 35 

 25 



Raritan Rose.... 



.5pt 



20 p. p. m__ 

 30 p. p. m_. 



May 7 



June 8 



...do... 



29 

 33 



38 



1 Naphthaleneacetic acid. 



the summer. This increase in hardiness is no doubt due to the greater 

 food reserves resulting from thinning at bloom time. 



Naphthaleneacetic Acid Thinning Sprays 



Attempts to thin peaches with naphthaleneacetic acid sprays at 

 the bloom or early postbloom period have given negative results. 

 Southwick. Edgerton, and Hoffman (38) reported that concentra- 

 tions of 10 to 40 p. p. m. of the sodium salt of naphthaleneacetic 

 acid or the methyl ester of naphthaleneacetic acid applied at full 

 bloom, petal fall, and 8 days after petal fall were of no value in 

 reducing the set of the Valiant and Elberta varieties. Similar re- 

 sults were obtained by Murneek and Hibbard (33) for Elberta and 

 several other varieties. Later Murneek 3 suggested that naphthalene- 

 acetic acid sprays applied about 30 days after bloom offered promise 

 for reducing the set of peaches. 



Naphthaleneacetic acid treatments 1 month after bloom were in- 

 cluded in several peach thinning tests in New York during the 1950 



3 Murneek. A. E.. in correspondence to M. B. Hoffman, Cornell University, 

 Ithaca. N. Y.. May 18. 1949. 



