ISHS Acta Horticulturae 636: XXVI International Horticultural Congress: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees
CHEMICAL REST BREAKING AGENTS FOR THE SOUTH AFRICAN POME AND STONE FRUIT INDUSTRY |
| Authors: | C. Costa, P.J.C. Stassen, J. Mudzunga |
| Keywords: | dormancy, apple, pear, cherry, plum, delayed foliation, hydrogen cyanamide, thidiazuron |
| Abstract:
Most of South Africa’s deciduous fruit is produced in areas which are climatically marginal, especially in terms of winter chilling, resulting in delayed foliation. Chemical rest breaking agents (RBAs) such as DNOC-winter oil have been used commercially with success on apples and pears in the past to ensure a greater uniformity in bud break and to alleviate problems associated with delayed foliation. DNOC is extremely toxic to man, harmful to the environment and was recently withdrawn from the market. Pressure from international markets has caused the Cape fruit industry to proactively move towards more eco-friendly production of fruit. This paper deals with the testing of safer, cost effective alternative RBAs to DNOC which had to be found in order for the South African deciduous fruit industry to remain viable. From the results of the various trials conducted over the past four seasons, regarding formulations, concentrations and timing of safer and cost-effective chemical rest breaking agents, hydrogen cyanamide (DormexR) at a low concentration (0.5% to 1%) in combination with a winter oil at 3 to 4% is now recommended commercially on apples. A new chemical, thidiazuron in an oil base (LiftR) will be registered in 2003 for use on apples, sprayed 5 to 6 weeks before expected full bloom at 3 to 4%, depending on chilling received and chilling requirement of cultivar. Promising results have also been obtained with LiftR on pears, cherries and plums. Future work will encompass longer-term effects on yields and interaction of RBA with chemical thinning procedures. | |
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