(Left): Pre-harvest drop during a 24-hour period in an unsprayed orchard. 

 (Right): Drop controlled by hormone spray. Photos by Robert L. Coffin. 



NAA applications) did not hasten 

 maturity as much as the earher 

 treatments and had Httle or no effect 

 on red color development. Where 

 late August treatments of 2,4,5- 

 TGPPA were made on Mcintosh, it 

 was possible to find apples fully red 

 and ripe on the trees three weeks 

 later. Such apples often contained 

 water core and were obviously unfit 

 for storage. In Gravenstein and 

 in Golden Delicious treated three 

 and five weeks before harvest, re- 

 spectively, the ripening effect of 

 2,4,5-TGPPA was not uniform on 

 the sprayed trees. Some fruits 

 were well colored and overmature, 

 whereas others were still green and 

 immature on the same tree. Also, 

 the same variety in different orch- 

 ards did not always respond to this 

 hormone in the same way for color 

 and maturity. 



Time Element Important 



It would seem, then, that we 

 should consider carefully the wis- 

 dom of using 2,4,5-TCPPA on large 



acreages of Mcintosh, even though 

 it may be the best drop control ma- 

 terial available. If the fruits sprayed 

 with this hormone are not harvested 

 within approximately two weeks af- 

 ter treatment, especially if tempera- 

 tures are high during the harvesting- 

 season, growers may find themselves 

 with some highly colored but soft 

 fruit with a short marketable life. 

 Since NAA materials can also has- 

 ten maturity to a lesser extent, fruit 

 sprayed with either material should 

 not be allowed to hang too long. 



If satisfactory results are being 

 attained with NAA materials, there 

 would be no reason to discontinue 

 their use for the control of apple 

 drop. If not, however, 2,4,5-TC- 

 PPA is a superior substitute for 

 drop control when properly timed. 

 We should, of course, recognize its 

 potential effect on maturity and har- 

 vest the crop accordingly. If has- 

 tened maturity is the aim, then this 

 new material offers some interesting 

 possibilities along this line, espe- 

 cially with early varieties. 



