Influence of Surfactants on the 

 Performance of ReTain as a 

 Harvest-management Tool on 

 Marshall Mcintosh Apples 



Duane W. Greene and James Krupa 



Department of Plant and Soil Sciences, University of Massachusetts 



Mcintosh is the most widely planted and most 

 miportant apple variety grown m New England. Our unique 

 set of environmental conditions allow Mcintosh to be grown 

 here better than almost anywhere in the world. One of the 

 shortcomings of this variety is that it can, and usually does, 

 display excessive preharvest drop. In an average year up to 

 25% of the fruit can be lost due to drop, while in severe 

 years, where above average temperatures are experienced 

 during the harvest season, over 50% of the fruit can fall 

 before they can be harvested. 



Various strategies have been employed to overcome 

 some of the deficien- 

 cies of Mcintosh. In 

 the 1940's it was 

 found that the chemi- 

 cal thinner 

 naphthaleneacetic 

 acid (NAA) could 

 also retard preharvest 

 drop. One applica- 

 tion was effective for 

 7 to 10 days and a 

 second application 

 gave an additional 7 

 days of drop control. 

 This compound is 

 currently registered 

 for controlling drop 

 of apples. While it is 

 sometimes effective 

 at controlling drop, 

 proper timing is im- 

 portant, ripening may 

 be advanced, and the 

 storage potential may 

 be reduced. The 

 discovery and ulti- 

 mate registration of 



Alar for control of preharvest drop on apples was an 

 enormous benefit to Mcintosh growers in New England. 

 However, the registration of Alar for use on apples was 

 withdrawn in the late 1980"s leaving growers only with the 

 somewhat inadequate NAA for drop control. 



Aminoethoxyvinylglycine (AVG) was developed as the 

 ReTain formulation following the loss of Alar as a harvest- 

 management compound on apples. In general, it has been a 

 very effective compound. However, relative to other 

 agrochemicals it is considered to be very expensive. Label 

 directions for ReTain contain the suggestion that specific 



54 



Fruit Notes, Volume 65, 2000 



