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shoots can occur. Later treatments were less effective because 

 the period of most rapid shoot growth is the 4-week period follow- 

 ing full bloom. Treatment more than 4 weeks after full bloom can 

 be expected to have little or no effect on terminal growth since 

 it has virtually ceased by this time. The importance of time of 

 application lies in the fact that in experiments of this type, one 

 usually finds that there is an inverse relationship between shoot 

 growth and flower bud initiation: the less shoot growth, the 

 greater the bloom the following year. 



Comparative Effectiveness of Treatments for Growth Suppression 



Mechanical and chemical treatments were compared for their 

 ability to suppress growth under our conditions. All treatments 

 did suppress growth (Table 2). However, limb spreading was less 

 effective than the other methods, and scoring, although effective, in- 

 jured the trees as evidenced by the season-long presence of red-bronze 

 colored foliage. Consistent, sizeable growth suppression was obtained 



Table 2. Effects of limb spreading, scoring, and growth regulators 

 on terminal growth of non-spur Delicious trees. 



Treatment^ 



Terminal growth (cm) 



Control 



Limb spreading 



Scoring 



Alar, 1000 ppm (1 lb/100) 



Ethephon, 500 ppm (1-2/3 pints/100) 



Ethephon, 1000 ppm (3-1/2 pints/100) 



Ethephon, 500 ppm + Alar, 1000 ppm 



Ethephon, 1000 ppm + Alar, 1000 ppm 



^Treatments applied 10-13 days after full bloom. A different set 

 of trees was used each year. 



^Means in the same column followed by different letters are signif- 

 icantly different at the 5% level. 



with 1000 ppm ethephon alone, and with 500 or 1000 ppm ethephon in 

 combination with 1000 ppm Alar-85* applied 10 to 13 days after full 

 bloom. Trees receiving these treatments looked like spur-type De- 

 licious. To date, the only adverse effect observed with these 

 chemical sprays applied 10-14 days after full bloom, has been the 

 killing of very weak spurs (less than S% of the total number of 

 spurs) with ethephon at 1000 ppm alone or combined with Alar-85*. 



Increased Bloom and Fruit Set the Year Following Treatment 



The scoring, limb spreading, ethephon and ethephon-plus-Alar- 

 85* treatments in 1973 increased bloom in 1974 but no treatment in- 

 creased fruit set (Table 3). Scoring in 1974 increased bloom but 



*Trade name 



