Le Thi Hoang Truc, Nguyen Van Son, Nguyen Ngoc Long, Nguyen Van Hoa
J.M. Campbell and R.A. Fullerton
The conventional dragon fruit production system in Vietnam involves plants growing up widely spaced concrete posts (‘mop top’ system). While it has low establishment costs, this system leads to a mass of cladodes of different ages at the top of the post. The plants are difficult to prune and there is poor spray penetration for control of pests and diseases, particularly canker. Over time the weight of the plant can break the support post. An alternative trellis-based production system (the T-bar system) is being introduced in Vietnam. The trellis uses a single (double) top wire and two spreaders down each post with each end supporting wires running the full length of the row. This system has many advantages over the conventional system. Cladodes from each leader can be trained, parallel to each other, down either side of the trellis resulting in a simple open, controlled canopy. Canker is the single greatest threat to the sustainability of dragon fruit production in Vietnam. A canker control protocol developed and verified by SOFRI calls for the removal of all infected cladode material from the canopy and the precision application of appropriate fungicides to the most susceptible parts of the plant (the young growing tips). The open canopy of the T-bar system allows excellent spray coverage for pest and disease control. Although the establishment costs of the T-bar system are higher than for the conventional system, field trials show that, with the precision canopy management possible with the T-bar system, yields per unit are of up to twice that of the conventional system. It is also possible that the fruit size and quality are consistently better. The T-bar system is superior to single wire trellis systems which will develop into single walls of dense overlying cladodes with disadvantages similar to those of the conventional system.