PRELIMINARY RESULTS FOR THE EVALUATION OF NEW REST BREAKING AGENTS ON TABLE GRAPES IN SOUTH AFRICA

Rest breaking agents play an important role in the production of table grapes in the early ripening regions of South Africa.
The use of rest breaking agents is often associated with uneven budburst, decreased fertility and poor bunch quality.
Hydrogen cyanamide (Dormex®, commercial product of SKW Trostberg, Germany) is the main rest breaking agent registered for use on vines.
Three trials were initiated on two Sultanina clone H5 (Vitis vinifera L.) vineyards in the Augrabies and Kakamas areas of the Lower Orange River region.
The rest breaking agent GAN (urea ammonium nitrate and calcium nitrate) together with various adjuvants (ACAR 92038, commercial product of Akzo Nobel Chemicals B.V., The Netherlands = Armobreak™ (worldwide trademark) = Partner® G (in South Africa) and ACAR97S21, development product of Akzo Nobel.) and application times, was evaluated and compared to a standard hydrogen cyanamide treatment.

Results showed that although the standard cyanamide treatment induced budburst earlier than GAN, these treatments did not differ regarding yield, quality and bunch ripeness at harvest.
GAN, in combination with the adjuvants, was most effective applied four and a half weeks before expected budburst.
Climatic conditions before budburst in the 1996/97 season were normal, but unseasonably cold and wet between budburst and harvest.
In 1997/98, conditions were cooler before budburst, but dry and warm until harvest.

These results indicate that GAN is effective on table grapes, when used in conjunction with the adjuvants tested.

XXV International Horticultural Congress, Part 4: Culture Techniques with Special Emphasis on Environmental Implications

P.J. Lombard, J.A. Viljoen, E.E.H. Wolf

hydrogen cyanamide, sultanina, table grapes, Vitis vinifera L., adjuvants, application time, GAN, ACAR 92038, ACAR 97S21, yield, bunch quality, budburst, climate, rest breaking agents, dormancy management, Lower Orange River region, South Africa

https://doi.org/10.17660/ActaHortic.2000.514.11