FRUIT THINNING WITH CHEMICAL SPRAYS 



27 



Table 7. — Effect of Elgetol thinning sprays on fruit size and yield 

 of several apple varieties grown in different fruit areas 



Variety 



Wealthy 



Golden Delicious 



Do 



York Imperial... 



Delicious 



Rome Beauty 



Winesap 



Delicious 



Year 



1941 

 1944 

 1944 

 1944 

 1946 

 1946 

 1945 

 1947 



Treatment 



'Check... 

 Elgetol.. 

 Check... 

 Elgetol.. 

 'Check... 

 Elgetol. _ 

 'Check... 

 Elgetol __ 

 'Check... 

 Elgetol. _ 

 'Check... 

 Elgetol.. 

 'Check. __ 

 Elgetol.. 

 Check... 

 Elgetol. _ 



Fruits per 



100 



blossoming 



spurs 



Number 



47 



27 



54 

 34 

 56 

 32 

 60 

 37 

 100 

 48 

 73 

 49 

 66 

 50 



Fruits 



per 



bushel ' 



Number 



182 

 124 

 200 

 150 

 220 

 170 

 198 

 144 

 134 

 111 

 113 

 81 

 121 

 110 

 86 

 79 



Yield 



per 



tree 1 



Bushels 



15 

 15 

 16 

 17 

 24 

 20 

 29 

 28 

 46 

 45 

 49 

 47 

 29 

 28 

 35 

 36 



State and 

 literature 

 reference 



New York {20). 

 ^NewYork(^). 

 -West Virginia (4) . 



Do. 

 Idaho (42). 



Do. 

 'Washington (5) . 



Do. 



1 In the Washington and Idaho experiments a standard apple box (containing 33 to 

 35 pounds of fruit) was used as the unit of measure. 



Golden Delicious. In the same experiments Elgetol was used, result- 

 ing in appreciable thinning on both varieties. 



The limited amount of work that has been done with the poly- 

 ethylene polysulfide and zinc dimethyl dithiocarbamate-cyclohexyla- 

 mine complex indicates that the results may be considerably more 

 variable than those obtained with other thinning agents. 



EFFECTS OBTAINED BY THINNING APPLES 

 WITH CHEMICAL SPRAYS 



Fruit Size and Yield 



In practically all cases where chemical thinning experiments have 

 been conducted increased fruit size has proved an outstanding re- 

 sult. Where the sprays have resulted in appreciable set reduction, 

 size difference between treated and check trees become apparent 

 within a few weeks following bloom. Typical data relating to the 

 effect of Elgetol sprays on fruit size in several areas are presented in 

 table 7. When the chemically thinned trees are compared with check 

 trees with no hand thinning (table 7 — New York, West Virginia, 

 and Idaho), differences are particularly outstanding. Much smaller 

 differences in fruit size were obtained in the Washington experiments 

 where the check trees were hand-thinned (35 to 50 days following 

 full bloom) and the chemically thinned trees were supplemented with 

 hand thinning if the crop appeared excessive. Such a practice doubt- 

 lessly accounts for the smaller differences that might be expected on 

 the basis of fruit-set reduction. In other Washington experiments 



