Hastening of Fruit Maturity of ‘Tsugaru’ Apples by Dichlorprop and MCPB

Abstract

Applications of dichlorprop (2, 4-dichlorophenoxy propionic acid triethanolamine salt) and MCPB (2-methyl 4-chlorophenoxy butyric acid ethyl ester) on ‘Tsugaru’ apples influenced their maturity and quality.
1. The degree of effectiveness of dichlorprop containing 0.3% adjuvant (Applauch BI) on fruit maturity was influenced by the timing and dosages of the spray. Among treatments made after 6 or 8 weeks after full bloom (AFB), the effectiveness was clearer in earlier applications at high dosages. However, high dosages of dichlorprop applied 4 to 8 weeks AFB suppressed fruit growth. Applications made 4 weeks AFB had no effect on fruit maturity but caused phytotoxicity, e.g., shoot dieback.
Considering the influence on fruit size, single or double sprays of 45ppm dichlorprop at 10, 12 or 10+12 weeks AFB seemed to be suitable for commercial usage. These treatments advanced fruit maturity 2 to 3 weeks and improved surface color.
2. Application of 50 or 67ppm MCPB sprayed 94 or 105d AFB advanced fruit maturity 1 to 2 weeks without causing phytotoxicity; whereas, 67ppm MCPB applied 85d AFB caused shoot dieback.
3. The addition of adjuvant (Applauch BI at 0.3%) increased the efficacy of dichlorprop in advancing fruit maturity and red color development. The beneficial effectiveness of dichlorprop was reversed by pretreatment with GA₄₊₇ which was sprayed 3 weeks AFB to promote fruit growth.
4. Application of lanolin paste, containing 5000ppm dichlorprop to the peduncle or abscission zone significantly advanced fruit maturity and anthocyanin formation but the same treatments on the bourse or bourse shoots had little effect on these harvest parameters.