ii^£ 





iV£iy HORMONE 



F. W. SOUTHWICK * 



FOR APPLE DROP 



MCINTOSH apple trees have 

 graced the rugged hillsides of 

 New England for many years, 

 lending a natural beauty to their 

 surroundings. Unfortunately, this 

 succulent variety is very apt to drop 

 one-fifth or more of its crop just be- 

 fore harvesttime. Since the Mcin- 

 tosh makes up 70 percent of the 

 present commercial apple crop, it is 

 easy to understand, then, how eco- 

 nomically important it is to avoid 

 as much loss as possible. 



2,4,5-TCPPA Superior 



With a view towards solving the 

 apple drop problem, the Station has 

 been carrying on tests for the past 

 year to compare the effectiveness of 

 a new hormone with that of NAA 

 (naphthaleneacetic acid) in the con- 

 trol of apple drop. This new hor- 

 mone goes by the impressive name 

 of trichlorophenoxypropionic acid, 

 better known as 2,4,5-TGPPA. It 

 seems that 2,4,5-TCPPA will con- 



■k Research Professor, Pomology. 



trol drop for a longer period and can 

 be applied slightly earlier than NAA 

 materials. 



According to tests with Mcintosh 

 apples, if the new hormone is ap- 

 plied at the same time or up to a 

 week before NAA materials are nor- 

 mally applied, it will give the best 

 drop control. If applied two weeks 

 ahead of NAA (usually about the 

 last day in August in Massachu- 

 setts), it tends to "run out" at about 

 the same time as NAA applied about 

 two weeks later. These results defi- 

 nitely point to the superiority of 20 

 parts per million of 2,4,5-TGPPA 

 over NAA, if it is applied at the 

 same time or four to seven days 

 ahead of the sound fruit drop. 



Hormone Reaction Varies 



When applied three weeks or 

 more before harvest, the new hor- 

 mone may improve surface red color 

 and hasten fruit maturity. Late 

 treatments of 2,4,5-TGPPA (at the 

 time or less than a week ahead of 



