Phenology and production of Carica papaya 'Honey gold' under cool subtropical conditions

Pietermaritzburg is a cool subtropical area, with light frosts in winter but high (>40 degrees C) temperatures in spring and summer. Papayas grow rapidly during the hot summer months but stop fruit set during the cold winter months, with fruits maturing the following spring and summer. A phenological model is presented which could be adapted to warmer subtropical areas. There is a limited "management window" in the sub-tropics. Cell division in fruits occurs pre-anthesis (one to two months) and post-anthesis (three to four months) with further fruit growth being by cell enlargement (six to eight months). To ensure uniformity of fruits, seedling selections were propagated by rooting leafy cuttings under intermittent mist with bottom heat. A superior female clone, 'Honey Gold', has been grown continuously by cuttings, for the past 40 years as viral diseases are not a problem in South Africa. Rooted cuttings start to set fruit close to the ground and subsequent crops are borne higher up the stems. Meantime side shoots develop and by regular pruning, in late summer, plants remain in production for eight to 12 years. Established plants produce 25-30 t/ha. Vegetative propagation by grafting is also successful and selection is underway for a red-fleshed bisexual clone with freckle-free skin. Because of leaf fall during and after the cold winters, fruits are exposed to sunburn from mid-winter to spring and damage occurs at surface temperature around 48 degrees C. Repeat sprays on the fruits with a white clay (kaolin) compound, reduces this damage. During the rainy season, regular fungicidal sprays are necessary to reduce fruit and leaf spot diseases. Regular fertilizer applications, including boron, and supplementary irrigation, ensure fruit set during the "management window". Although climatic conditions are marginal for papayas in this area, the production of uniform, good quality fruits has been economically successful. 'Honey Gold' fruits are more tolerant to anthracnose fruit spot disease and seldom develop unsightly "freckle" spots on the golden skin.