Effects of trellising, crown bunch handling, and the number of oil emulsion and gibberellic acid sprays on harvest-pruned sultanas

Abstract

Effects of trellising together with the use of various foliage wire arrangements on the production and quality of harvest-pruned sultanas were studied over 4 years. In one experiment a single wire and four narrow 0.4 m 'T' trellis systems, and in a second experiment four 0.9 m wide 'T' trellis and one 0.4 m narrow 'T' trellis system, were tested. Other treatments superimposed on all trellises included crown bunch removal in early spring or at harvest pruning, one and two alkaline oil-in-water sprays (oil sprays) and gibberellic acid (GA) or no GA spray. There were no differences between the four narrow trellises. Dried fruit yield of these four trellises was greater than that of the single wire by an average of 27%, because of higher bunch and cane numbers. There were also no differences between the four wide trellises except that two of the complex ones had more canes. The narrow trellis NTI (used in both experiments) yielded 27% less than the wide trellises because of fewer bunches per vine, caused by lower cane numbers and fruitfulness. Trellising had no effect on fruit quality and only marginal effects on rate of fruit drying, most probably due to low vigour of the experimental vines. As the complex trellis systems had no advantage over the simpler two wire 'T' trellises, their use in harvest pruning is not advocated. In both experiments two oil sprays produced slightly better fruit quality with faster drying of fruit. Use of two oil sprays is warranted where fruit has to be dried rapidly to minimise risk due to rain damage. Early crown bunch removal did not reduce yield and the best time for bunch removal was 6 weeks after bud burst. Use of GA in harvest pruning is not recommended as it does not improve fruit quality and in some years leads to slower fruit drying.

The Swing-Arm Trellis for Sultana Grapevine Management

“…Shaulis & May 1971, May, Sauer & Scholefield 1973, Scholefield, May & Neales 1977, Sarooshi & Roberts 1979, or by increasing the height of the canopy by encouraging the replacement shoots to grow upward (May 1966, Scholefield, May & Neales 19791980 1977, Baldwin et al 1979). Preliminary evidence from other experiments suggests that the S-vines will not suffer as a consequence of the increased yield and reduced vigour of the fruit-bearing shoots.…”

“…On the other hand, the greater number of non-cane bunches would increase the cost of trellis-drying as they would have to be picked separately by hand. Their removal before flowering, perhaps combined with positioning and thinning of the cordon-shoots, maybe advantageous as has been suggested for standard vines by Sarooshi and Roberts (1979). Crop reductions incurred in this way could be avoided by leaving additional nodes on the canes.…”

Effects of varying the method of applying alkaline emulsion on the drying of Sultana grapes

“…The experiments here described were carried out during harvest season 1977 (experiments 1, 2), 1978 (experiments 3-57, 8) and 1981 (experiments 6,9) on Sultana berries collected in the vineyard of the CSIRO Division of Horticultural Research at Merbein, Victoria. In 1977, the berries were harvested at advanced maturity in late May while those for the 1978 and 1981 experiments were collected thoughout the season and thus varied widely in their state of ripeness.…”

Chemical Removal of Cordon Bunches in Dried Grape Production

“…Several plant growth hormones and fertilisers have demonstrated berry thinning effects on grapevines over a range of development stages (Weaver & Pool, 1971a;Weaver, 1975;Sarooshi & Roberts, 1979;May, 2004). Plant hormones, for example gibberellins (GAs), cytokinins and auxins have been shown to promote or inhibit flowering and fruit-set.…”

“…GAs, which play a vital role in overall plant development (Swain & Singh, 2005), promotes formation of the anlagen and the growth of tendrils, but inhibits the growth of the inflorescence primordia (Srinivasan & Mullins, 1980;Boss & Thomas, 2002). With the introduction of the trellis drying technique, GAs were employed as bunch thinning sprays to improve penetration of drying oil and reduce oxidative browning in berries (Lynn & Jensen, 1966;Sarooshi & Roberts, 1979). However, application of GAs can reduce shoot numbers in the following season by causing bud necrosis (May, 2004).…”