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reduced the ethephon effect. Ethephon alone at 500 ppm or lOQO ppn^ 

 or ethephon at 500 ppm plus Alar-85* at 1000 ppm suppressed fruit 

 size. None of the treatments increased repeat bloom in 1975. 



Mcintosh . Post-bloom sprays of ethephon were applied on July 22 

 and August 8 on this cultivar. Ethephon at 1000 ppm applied on 

 July 22 eliminated the crop and 500 ppm thinned excessively, whereas 

 trees receiving 250 ppm ethephon on July 22 lost only 16^ of their 

 crop and averaged 68^ red color on fruit by August 28. Ethephon 

 applied at 75, 125, or 250 ppm (1/4, 5/12 and 5/6 pt/100 gal) on 

 August 7, enhanced red color development and only the highest con- 

 centration caused excessive drop by August 28. All concentrations 

 of ethephon on both dates increased soluble solids (sugar content) 

 and decreased flesh firmness. This advancement in fruit maturity 

 was confirmed by respiration data. The ethephon sprays as on 

 Early Mcintosh and Cortland failed to enhance repeat bloom in 1975. 



Red Delicious . Ripening of this cultivar also was stimulated by 

 ethephon. Both 500 and 1000 ppm caused fruit drop and all concen- 

 trations advanced watercore development and suppressed fruit size. 

 Alar-85* was capable of reducing the ripening effects but caused 

 further fruit size suppression. 



A loss of flesh firmness which usually accompanies ripening 

 did not occur with the ethephon- treated fruit, probably due to the 

 presence of water core. The watercore in the fruit tissue may have 

 increased the resistance to the plunger of the pressure tester. 



The ethephon and ethephon plus Alar-85* sprays, with the excep- 

 tion of ethephon at 250 ppm, increased repeat bloom in 1975 but no 

 treatment increased fruit set. 



Conclusions 



Increased flower bud initiation is not a consistent response 

 of apple cultivars to post-June drop applications of ethephon. Sum- 

 mer applications of ethephon can advance harvest date but the ques- 

 tion is can it be done consistently without excessive fruit 



drop? Our 1975-1976 studies may help to answer this question, but 

 even if feasible, the value of the advancement is questionable. We 

 generally are not concerned about advancing the maturity of Cortland 

 and Delicious since the harvest of these cultivars is usually de- 

 layed until Mcintosh harvest is nearly complete, and therefore, they 

 are often overmature. The use of ethephon might aggravate this prob- 

 lem. Fruit size on Mcintosh trees harvested the 3rd or 4th week of 

 August might be excessively small except on young trees or those 

 with a light crop. Thus, it appears that mid-July or early-August 

 applications of ethephon have little value when one considers the 

 risk of excessive fruit drop, loss of fruit size or advanced matur- 

 ity. Present recommendations for ethephon' s use which permits the 

 harvest of Mcintosh in the first week of September appears to be 

 a safer practice. 



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*Trade name 



