7 - 



Scoring is an age-old technique in which the bark is cut to 

 the wood all the way around the trunk of a tree. This manipulation 

 restricts terminal growth of the tree and increases flower bud ini- 

 tiation, and may thereby increase fruiting the following year. 

 Limb-spreading is another technique to restrict terminal growth and 

 encourage flowering and fruiting. Vegetative growth may also be 

 restricted by application of some plant growth regulators, which 

 are known to induce flowering under some conditions. During the 

 past 3 years, we have been comparing the abilities of these tech- 

 niques to restrict growth, encourage flower bud formation, and in- 

 crease fruit set on young Delicious apple trees at the Horticultural 

 Research Center in Belchertown. 



Timing of a Growth Regulator Spray for Growth Suppression 



A combination of Alar and ethephon applied early in the grow- 

 ing season can markedly suppress vegetative growth on apple trees, 

 and has been reported to encourage flowering on young trees. To 

 test its effectiveness on young Delicious trees in Massachusetts, 

 a combination of Alar-85* (750 ppm) and ethephon (600 ppm) was ap- 

 plied at about 10-day intervals throughout the growing season. The 

 effects of the treatments on terminal growth are shown in Table 1. 



Table 1. Effect of a spray mixture containing 600 ppm ethephon and 

 750 ppm Alar-85* on terminal growth of spur-type Delicious 

 trees when applied at different intervals after full 



bloom, 1975. 



Time of application 



(days after full bloom) ^ Terminal growth (cm) 



Check 44ab>' 

 2 31d 

 11 25e 

 22 31d 

 32 36c 

 43 41bc 

 53 42b 

 64 42b 

 74 41bc 

 85 45ab 

 95 44ab 

 107 47a 

 n6 45ab 



^Full bloom May 19, 1975 



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

 icantly different at the 5% level. 



Greatest shoot suppression occurred when the growth regulators 

 were applied about a week and a half after full bloom. Treatment 

 earlier than this was less effective because regrowth of suppressed 



*Trade name 



