Effect of aminothoxyyinylglycine (AVG) on preharvest drop, fruit quality, and maturation of 'McIntosh' apples. II. Effect of timing and concentration relationships and spray volume

AVG was evaluated for its effect on controlling preharvest drop and influencing ripening of 'McIntosh' apples in Maine and Massachusetts. AVG consistently and effectively retarded preharvest drop. AVG was superior to NAA and comparable to daminozide in drop control. Dilute or 2x applications were more effective than applications made at lower water volumes. One application of AVG made 4 weeks before anticipated normal harvest was more effective in controlling preharvest drop than split applications of the same amount made earlier or later. In general, AVG delayed ripening as assessed by a retardation in the development of red color, maintenance of flesh firmness, delayed degradation of starch, and a delayed onset of the ethylene climacteric. We conclude that AVG is an effective drop control compound that is also useful as a management tool to extend the harvest window for blocks of 'McIntosh' that would otherwise ripen simultaneously. Chemical names used: aminoethoxyvinylglycine (AVG), naphthaleneacetic acid (NAA), succinic acid-2,2-dimethylhydrazide (daminozide, Alar).