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 fruit are lost as tertiary and quaternary fruit can never equal them in size. 



—William J. Lord 



I I I I I I I I I I I I I I I I 



PREHARVEST DROP CONTROL OF APPLES FOR 1961 



It is now apparent that many growers in Massachusetts have trees with mod- 

 erate to heavy sets of apples. Trees of varieties that are prone to drop fruit 

 at harvest time generally suffer greater percentage losses when they are carrying 

 a heavy crop than comparable trees producing a moderate yield. In other words, 

 the possibilities for a heavy preharvest drop of such varieties as Mcintosh and 

 Baldwin are greater in heavy crop years like this one than they were in 1960 

 when the average set of fruit was lighter. Of course, temperature, nitrogen 

 level, moisture supply and foliage condition at harvest time are other important 

 factors which can markedly influence drop in spite of crop size. 



Since last year both NAA and 2,4,5-TP have been cleared by the Pure Food and 

 Drug Administration for use on apples for preharvest drop control. The compound 

 2,4,5-TA is no longer available for this purpose, however, since no attempt was 

 made to have it cleared. 



Napthaleneacetic acid (NAA) can be used at the maximum dosage of 20 ppm (up 

 to 35 grams per acre) and applied no more than twice (a 0.2 per cent dust is 

 equivalent to a 20 ppm spray). NAA cannot be applied within 5 days of harvest. 

 The material has a 1.0 ppm tolerance. These requirements are sufficient to sat- 

 isfy our recommendation of the past several years for preharvest drop control of 

 Mcintosh for a period of about 3 weeks. In other words, two applications of NAA 

 at 20 ppm will control Mcintosh drop for about 3 weeks with a minimum amount of 

 hastened ripening if the two applications are made about 10 days apart. 



Now that CA storage is an important part of the Mcintosh deal, it may be 

 possible to pick the CA Mcintosh before applying NAA for drop control in some 

 years. It is now known that CA Mcintosh should be picked first (when they have 

 sufficient color to meet U. S. Fancy grade requirements and at 15 to 17 pounds 

 firmness. Consequently, it may be possible to spot pick the fruit for your CA 

 rooms before preharvest drop is of any consequence and delay the initial NAA 

 application until the CA Mcintosh are picked. Of course, Mcintosh drop may reach 

 serious proportions in early September occasionally and in such years the use of 

 NAA may be necessary before CA Mcintosh harvest. 



Since NAA cannot be applied within 5 days of harvest a considerable amount 

 of advance planning concerning application of NAA to individual blocks should be 

 done by growers of large quantities of Mcintosh. If such advance planning is 

 not done a grower may easily find himself in the position of either being unable 

 to pick certain blocks of Mcintosh, while waiting for 5 days to elapse after an 

 NAA spray, or because of the immediate necessity for picking, allow a block to go 

 unsprayed and suffer whatever natural drop losses occur. 



2,4,5-trichlorophenoxypropionic acid (2,4,5-TP), at a 20 ppm dosage is the 



