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Rest breaking agents and application date affect bud break but not yield of 'granny smith' and 'Royal Gala' apple

Author:
North, M. S., De Kock, K., Booyse, M.
Source:
Acta horticulturae 2014 no.1058 pp. 639-644
ISSN:
0567-7572
Subject:
apples, application timing, budbreak, chemistry, cold treatment, cultivars, farms, fruit trees, knapsack sprayers, oils, orchards, shoots, urea
Abstract:
Rest Breaking Agents (RBA) are used to reduce the negative effects of insufficient winter chilling. Their effectiveness depends on application date, concentration, chemistry and cultivar. In a four year study, RBA were applied five to six times between early August and late September to single-tree plots within mature commercial Royal Gala (RG) and Granny Smith (GS) apple orchards on the same farm. The results from the final year are presented here. Either Dormex®/oil (0.5%/4% v/v), Symphony® (16% N), Oil (5%), Oil/Oil (5%/5% one week later), GAN/Partner® (5%/2%) or Oil/Urea (5%/5% m/v) were applied using motorized knapsack sprayers. Control trees were left untreated. Bud break (BB) on one-year-old pre-marked shoots and fruit/tree and kg/tree were recorded. In GS, Oil and Oil/Urea on the second date (25/8/11); Symphony®, Oil/Oil, GAN/Partner® and Oil/Urea on the third date (7/9/11); DM/Oil, Symphony and GAN/Partner® on the fourth date (21/9/11) and GAN/ Partner® on the fifth date (27/9/11) improved BB relative to the control. No RBA affected yield. Trees receiving the first application (10/8/11) had more fruit/tree than the control. In RG, Symphony®, Oil/Oil and Oil/Urea treatments had higher BB than the control. Higher BB occurred after the third application (7/9/11) than after the first (10/8/11), fourth and fifth applications. In the first harvest, DM/Oil and Oil/Oil treatment trees had higher kg/tree, and the Oil/Urea treatment lower kg/tree than the control. Neither RBA nor application date had any effect on total fruit/tree, kg/tree or fruit size. Although some treatments promoted BB, the final yield of either cultivar was not affected.
Agid:
1204340