FRUIT THINNING WITH CHEMICAL SPRAYS 



35 



season. The results are given in table 10. The thinning obtained in 

 these trials as compared to the lack of effect from bloom and early 

 postbloom treatments mentioned above may be due to the greater leaf 

 surface present when the later treatments were applied and hence 

 greater absorption of the hormone. On June 8 when the naphthalene- 

 acetic acid treatments were applied, the trees were in heavy foliage 

 but the terminal buds had not formed and shoot growth was still 

 active. At this time there was no indication of the beginning of 

 the June drop. 



The greater fruit set recorded for the check trees (table 10) from 

 June 8 to July 10 represents the normal June drop for these varieties 

 under the conditions of these tests. In all cases the hormone sprays 

 resulted in a greater increase in drop, the magnitude of which was 

 related to the concentration of the spray. On July 10, when the 

 June drop was over and the final set counts were made, there was 

 a noticeable difference in size of fruits on trees receiving the various 

 treatments. This size difference is illustrated by the average weight 

 of 100 fruits taken at random from each of the 8 trees in each 

 treatment. 



The data in table 10 also show that the amount of thinning re- 

 sulting from any given concentration of naphthaleneacetic acid 

 varied considerably with the variety. The most satisfactory results 

 were obtained with 15 p. p. m. on Golden Jubilee, 20 p. p. m. on 

 Raritan Rose, and 30 p. p. m. on Halehaven. It is conceivable that 

 for any given variety the results may vary from one year to another, 

 depending upon environmental conditions that influence tree growth 

 and fruit set. 



Table 11. — Effectiveness of Elgetol thinning sprays on Bartlett pear, 

 at Wenatchee, Wash., 194,7-48 



Orchard and 

 treatment 



Concen- 

 tration 

 per 100 

 gallons 



Date sprayed 



Bloom stage 



Fruits 



per 100 



blossoming 



spurs 



Reduction 



in fruit 



set 



Kane orchard: 

 Check (1947)_ 



Pints 







Number 



100 



66 

 65 

 68 

 59 



7 

 4 

 2 



22 

 17 

 13 



42 

 32 

 29 



Percent 



Elgetol 



Do 



Do 



Do 



Muffley orchard: 

 Check (1948). 



1 



2 



1 



2 



April 12, 1947 

 do 



April 14, 1947_ 

 do 



Full bloom 



do 



Early petal fall 

 do 



34 

 35 

 32 

 41 



Elgetol 



Do 



Nichols orchard: 

 Check (1948) 



1 



2 



May 9, 1948_. 

 do 



Full bloom 



do 



43 



71 



Elgetol 



Do_ 



Peterson 



orchard: 

 Check (1948). 



1 



2 



May 4, 1948. 

 do 



Full bloom 



do 



23 



41 



Elgetol 



Do 



1 

 2 



May 10, 1948. 

 do 



Full bloom 



do 



24 



31 



