Innovative production systems for the Australian custard apple industry

Abstract

Many new technologies have been or are currently being developed to improve yield and fruit quality of custard apple. The most important of these new technologies is training of trees onto an open Tatura trellis system at tree densities twice the conventional, open vase system (800 vs. 400 trees per hectare). Use of the open Tatura trellis system has only been made feasible since the availability of new, very high fruit-setting varieties such as KJ Pinks, where up to 40% of flowers set fruit. Other innovative management practices are also being incorporated into a complete management package. They include the use of dormancy-breaking chemicals, chemical growth retardants and leaf tipping and stripping. Leaf stripping is a useful technique to increase late flowering and fruit set. This technique, if done at the appropriate time during early summer, releases the sub-petiolar buds (buds below the leaf stalks), increasing and in some cases doubling, the number of new season laterals and flowers. Leaf stripping involves removing 5-10 terminal leaves, including the tip (about the last third depending on shoot length). Excessive vegetative growth has been shown to reduce fruit set and significantly increase the severity of the internal fruit disorder called ‘woodiness’. Shoot growth greater than 60cm is deemed excessive. The growth retardant, uniconazole (Sunny®) has been shown to effectively control vegetative growth in custard apple. Two applications of this growth retardant during the first vegetative flush reduced shoot extension growth by about 20% and increased flowering by about 30%.