conditions for initial fruit set. All the blossom thinners 

 were effective in reducing the initial fruit set and 

 number of fruit per flower cluster during this period. A 

 prolonged period of heavy cloud cover from June 1 3 to 

 June 17, 1998 resulted in heavy June drop for all the 

 trees in this study. This episode of fruit drop 

 commenced on June 23, and was more severe than the 

 fruit drop caused by blossom thinners. Much of the 

 potential effect of chemical thinners on yield and fruit 

 characteristics at harvest was obscured by this natural 

 fruit drop. 



The most effective blossom thinner, Wilthin, 

 caused severe phytotoxicity and fruit russet. Future 

 studies should address this concern by evaluating the 

 effect of lower rates of Wilthin. These data indicate 



that blossom thinners show some promise. More study 

 is needed to select the best chemicals and to optimize 

 their use. 



Evaluation in Massacliusetts 



Materials & Methods 



A block of mature Marshall Mclntosh/M.26 apple 

 trees growing at the University of Massachusetts 

 Horticultural Research Center, Belchertown, MA 

 were selected. Treatment trees were selected so that a 

 buffer tree was located on each side of a treatment tree 

 to prevent spray drift. Prior to bloom 2 limbs per tree, 

 1 to 15 cm in diameter, were selected and tagged. At 



Fruit Notes, Volume 67, Spring, 2002 



11 



