11 



Table 3. Effects of Promalin at different concentrations on fruit 

 thinning of 'Red Prince Delicious' apples. 1979. 



Treatmen t 



Fruit/ 



Sevin cm limb circ. 100 blossom clusters 



1. Check 



2 . Promalin 25 



3 . Promalin 25 + 



Glyodin 1 pt/ 

 100 gal. 



4. Promalin 50 



5. Promalin 100 



+ 



5.2a" 

 3. 3abc 



4. Sab 

 3.5ab 



3.2bc 



2 .9bc 



2. 3cd 

 1. 7cd 



0. 7d 

 0.6d 



60a 

 4 3abc 



45ab 

 36bc 



41abc 



31bc 



25bcd 

 23bcd 



9d 

 7d 



Treatments applied May 10, 1979 at full bloom. 



r 

 Sevin 1/2 lb/100 gal was applied to 1 limb per tree on June 1, 1979. 



c 



Numbers in a column followed by a different letter are significantly 

 different at odds of 19 to 1. 



Variable Promalin Responses 



Another concern of Promalin users in Massachusetts is the lack 

 of a consistent and predictable response. Sometimes fruit from Pro- 

 malin- t rea ted trees are similar to those from untreated trees; in 

 other years Promalin causes significant fruit elongation. It is our 

 feeling that Promalin always elongates fruit, provided that it was 

 applied near full bloom. Why then is there a variable response? 

 Promalin promotes at least 2 independent processes: fruit elongation 

 and fruit thinning. We believe that Promalin thins off elongated 

 fruit early in the season in the years when it appears not to be 

 effective. However, further observation will be necessary to confirm 

 this . 



Suggestions for Promalin use in 1980 



Calibrate your sprayer. Thinning due to Promalin has often been 

 traced to overapplicat ion because of improper sprayer calibration 

 and nozzle adjustment. The margin of error with Promalin is not 

 great. The label suggests that Promalin should be applied in 

 100-200 gal/acre. Therefore, an error in application of only 

 50 gal/acre can result in a 50% increase in the amount of Pro- 

 malin applied. 



