|Authors: ||M.B. Currie, K.J. Patterson, W.P. Snelgar, P. Blattmann|
|Keywords: ||kiwifruit, girdling, 'Hayward', 'Hort16A', 'Zesy002', extension|
Girdling, otherwise known as cincturing or ring barking, was tested for its ability to improve yield and quality of Actinidia chinensis var. deliciosa ‘Hayward’, A. chinensis var. chinensis ‘Hort16A’ and, more recently, A. chinensis var. chinensis ‘Zesy002’ kiwifruit grown commercially in New Zealand.
Originally, we developed girdling of individual 1-year-old fruiting canes as a technique to increase fruit size for organic kiwifruit growers.
However, the technique was rapidly adopted by growers of conventional kiwifruit.
Girdles healed rapidly within 3-6 weeks of application, and plants recovered fully.
Cane girdling was largely superseded by girdling of the main trunks, which resulted in similar benefits to cane girdling, but was faster to apply, responses were larger, and there was less variability of fruit characteristics within vines.
However, there was some risk of negative plant responses if girdles were applied too deeply, so that the xylem tissue was damaged, or when girdles were applied late in the growing season.
In both of these cases, girdles did not always heal before winter, and development of leaf canopies in spring was retarded.
Timing of girdle applications was critical for response.
Girdles applied soon after fruit set, during the rapid phase of fruit growth, increased fruit weight, while those applied during the starch accumulation phase increased dry-matter content of fruit and improved the eating quality of fruit.
Girdles applied in autumn increased bud break and flower numbers of vines in the following season.
The story of how girdling was developed for New Zealand kiwifruit growers is also an informative case study.
It demonstrates that a significant extension plan is required for the rapid adoption of even a relatively simple new technology by a horticultural industry.
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