Effects of AVG and NAA on preharvest fruit drop and quality of apple cultivar Idared

In some production years, apple cultivar Idared may be prone to preharvest fruit drop and therefore yield lost. In this research, effects of AVG (aminoethoxyvinylglycine) and NAA on preharvest fruit drop and fruit quality of Idared, in two different orchards and application dates were investigated. Applied chemicals were VBC 30033 (4,15% AVG, Valent Biosciences, USA) at rate 3,0 g/l, Fixormon (8,5% NAA, Cifo, Italy) at rate 0,24 ml/l and Dirager (3,3% NAA, L-gobbi, Italy) at rate 0,6 ml/l. Applications were done 28 days (VBC 30033 and Fixormon) and 14 days before anticipated harvest date (Fixormon and Dirager). The most effective were AVG treatments, as percentage of fruit drop was the smallest in both orchards. AVG was effective during whole ripening period of 6 weeks. AVG treatments were not consistent in delaying fruit ripening. NAA was effective during the period of two weeks after the treatment. After that period fruit drop was more intensive than in control trees. NAA decreased fruit firmness and increased starch degradation and soluble solids content in both orchards. It is recommended that NAA treatments should be repeated in order to prevent fruit drop until optimum harvest date. NAA applications may lead to decreased storage potential of fruits in case of harvest is delayed beyond optimum harvest date.