Effects of Aminoethoxyvinylglycine (AVG) on Preharvest Fruit Drop, Maturity, and Cracking of Several Apple Cultivars

Aminoethoxyvinylglycine (AVG) applied 2 to 6 weeks before the optimum harvest date dramatically reduced preharvest drop of several apple cultivars (Malus domestica Borkh). AVG sprays reduced the loss of fruit firmness and starch particularly in harvests after the optimum harvest date. The development of water core was delayed in ‘York’, and maturity cracking was delayed or prevented in ‘Rome’ and ‘Golden Delicious’ by AVG. Color development was delayed by AVG for summer cultivars, ‘Redfree’ and ‘Gala’, and for ‘Golden Delicious’, but did not have an influence on red color of ‘Rome’ or ‘York’. Soluble solids concentration (SSC) was generally unaffected. Equivalent dilute airblast concentration (EDAC) of AVG at 44 mg·L−l was more effective than a standard rate of NAA for control of fruit drop for ‘Golden Delicious’. For ‘Law Rome’, an AVG rate of 66 mg·L−1 was more effective than NAA, but for ‘York’ these rates gave similar control of drop as NAA. AVG at 132 mg·L−1 ED AC and above was more effective than NAA for all cultivars tested. The use of Regulaid or Kenetic surfactants did not affect AVG responses; however, the sili-cone surfactant, ABG 7011, enhanced the effectiveness of AVG. When fruit were left on the tree for periods of 3 to 5 weeks after the optimum harvest date, NAA enhanced softening, reduced starch, and increased water core of ‘York’ and increased maturity cracking of ‘Golden Delicious’ and ‘Law Rome’. SSC and red color were generally unchanged by NAA. Chemicals used: Aminoethoxyvinylgly-cine hydrochloride (N-(phenylmethyl)-lH-purin-6-amine, (AVG)); potassium salt of napthalene acetic acid (NAA, K-200); trisiloxane ethoxylate methyl ether (an organosilicone surfactant, ABG 7011).