19 



It was found that the greater the number of blossom clusters at bloom the 

 more fruit that remained after June drop (Figure 1). However, the point that 

 we would like to e;iipluisize is that it requires a large increase in the amount 

 of bloom on a limb to cause a relatively small increase in fruit number. For 

 example, if the bloom on a limb was increased from 5 to 10 blossom clusters per 

 cm limb circumference, the fruit set after thinning would increase only from 

 about 5.5 to 6.5 fruit per cm limb circumference. NAA at 2.5 ppm plus J lb. 

 carbaryl per 100 gal. is a moderate thinning treatment, and adequate thinning 

 was obtained on limbs with blossom densities up to 10 to 12 blossom clusters 

 per cm limb circumference. NAA at 5 to 7.5 ppm plus carbaryl would have been a 

 better choice for the limbs having a heavier bloom. 



5 10 15 20 25 



Blossom Clusters per cm Limb Giro. 



30 



Figure 1. Effect of blossom cluster density on final fruit set of Mcintosh 

 apples following a chemical thinning spray of NAA at 2.5 ppm plus 1 lb carbaryl 

 (50 % WP) per 100 gal. 



Although blossom density does influence fruit set, treatments can be 

 selected that will operate effectively over a relatively wide range of 

 densities. NAA at 3 ppm plus carbaryl at 1 lb. per 100 gal. should be 

 effective on trees with low to moderate bloom, whereas NAA at 5 to 7.5 ppm plus 

 carbaryl at 1 lb. per 100 gal. would be more appropriate on Mcintosh trees with 

 a moderate to heavy bloom. 



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