Identification of phenological growth stages of sugar apple (Annona squamosa L.) using the extended BBCH-scale

Codes and detailed crop-specific descriptions are presented for the growth stages of the sugar apple tree (Annona squamosa) in southern China, which contributes to the standardization of national and international testing systems for fruit growth. The codes used in this work are a three-digit numerical system that describes the growth stages of the sugar apple tree as based on the extended Biologische Bundesantalt, Bundessortenamt, and Chemische Industrie (BBCH)-scale. A total of eight principal growth stages are described: (0) bud, (1) leaf, and (3) shoot development, (5) inflorescence emergence, (6) flowering, (7) fruit development, (8) fruit maturity, and (9) senescence. The use of the BBCH phenological scale presented in this work for application to A. squamosa will assist in the development and implementation of agronomic management protocols and be valuable for future research into any of the plant's developmental stages.