due to the increase in pygmy fruit produc- 

 tion. 



The combination of Accel with Sevin 

 emerged again as a good thinning combina- 

 tion. The combination of NAA with Accel 

 was not acceptable because it increased 

 pygmy fruit formation without thinning. The 

 Accel and NAA combination on Delicious 

 produces a similar undesirable response and 

 thus it is not recommended. We previously 

 have combined NAA and Accel on Mcin- 

 tosh with acceptable thinning and no adverse 

 effects on fruit size or fruit characteristics. 

 As a rule-of-thumb, however, we suggest that 

 Accel and NAA should not be applied to- 

 gether on any apple that has Delicious as a 

 recent parent. Perhaps there are other culti- 

 vars that also react adversely to this combi- 

 nation but they are yet to be identified. 



1994 Thinning Results with 

 Other Cultivars 



Accel did not thin Gala when 37 ppm was applied 

 at petal fall or at 10 mm diameter Combination of 

 Sevin with Accel did not improve the thinning of Accel. 

 Accel did not improve fruit size. NAA at 6 ppm plus 1 

 qt Sevin XLR/100 gal severely over thinned Gala. 



Accel did not thin Delicious when applied at the 10 

 mm stage at concentrations between 42 and 84 ppm. 

 The addition of Sevin did not improve the thinning re- 

 sponse above Sevin alone. Accel did not increa.se fruit 

 size. 



Suggestions for the Use of Accel in 1995 



Accel performed erratically as a thinner in 1994; 

 however, there may be several reasons for this result. 



Concentration 



There is a large body of experimental evidence gath- 

 ered over the past 15 years to suggest that the active 

 ingredient in Accel, BA, thins in a linear manner It is 

 critical to know the.concentration being applied and to 

 be aware of the concentration of BA that can cause 

 effective thinning. In general, Accel will not thin sig- 

 nificantly at concentrations below 25 ppm. The effec- 

 tive thinning range for easy-to-thin cultivars such as 

 Empire, Idared, Rome, and possibly Mcintosh is 50 to 



75 ppm. Hard-to-thin cultivars such as Delicious or 

 Golden Delicious may require 75 to 100 ppm. 



In 1994 the label limited application of Accel to 20 

 g a.i./acre or two applications that did not exceed 40 g 

 a.i./acre. The label has been changed for 1 995 to allow 

 up to 30 g a.i./acre per application and two applica- 

 tions totaling no more than 60 g a.i./acre. An increase 

 in the amount applied may result in better thinning. 



Steps to Determine the Rate of Accel 



1 . Calculate the tree row volume and dilute gallonage 

 requirement of the block of trees to be thinned. 



2. Select the concentration of Accel that is appropri- 

 ate for thinning the block. 



3. Determine if you can apply the concentration re- 

 quired to thin the block and still be within label 

 limits (Table 4). 



For example, assume that you have a block of ma- 

 ture Mcintosh on M.7 that require 300 gal/acre for a 

 dilute spray. If you put the total amount of Accel in 

 that you are allowed to apply at one time, 30 g a.i. in a 

 tank with 300 gal of water, you will end up with a con- 

 centration of 26 ppm, a level near the minimum con- 

 centration to get a thinning response. The chances of 

 getting a good thinning response from Accel alone at 



Fruit Notes, Spring, 1995 



