Ethephon use to control vigour, reduce shade and improve fruit quality in Vitis vinifera cv. Cabernet Sauvignon

Abstract

Ethephon as 'Ethrel' was applied to vigorous Cabernet Sauvignon grape vines to investigate its reported effect on reducing vegetative growth and consequently reducing within canopy shade and advancing and improving fruit quality. Two trials were established. Vines had either shoots vertically positioned between wires or previously unpositioned vines were hedged. Four treatments included non-sprayed vines and three treatments of 600 mg.1⁻¹ (active ingredient) ethephon applied at: three weeks (early). Six weeks (late) and, three and seven weeks (double) post bloom, to the upper third of the vines on both hedged and positioned vines. Leaves were removed from the fruit zone in half the vines of each ethephon treatment.

All ethephon treatments significantly inhibited growth in all vines. Shoot tips were aborted and lateral buds prevented from bursting. Timing of ethephon application determined the extent of inhibition. The early application inhibited all lateral growth for one month. Not all lateral growth was inhibited by the late application. The double application inhibited growth for three months. In the fruit zone the number of leaves was significantly lower due to ethephon in both trials and a greater percentage of fruit was exposed in hedged vines.

Fruit was sampled at weekly intervals from veraison (23.3.91) to harvest (26.4.91) and changes in fruit composition measured. Ripening was advanced in all ethephon treated fruit in vertical shoot positioned vines due to significant increases in soluble solids and decreases in titratable acids, compared, to non-sprayed. The pH was unaffected. Anthocyanins and phenols were significantly increased in all ethephon treatments after veraison but increases were significant for the double spray only at harvest. For hedged vines, ripening was not significantly advanced and anthocyanins and phenols were not significantly different from the non-sprayed at harvest. pH was significantly different between treatments but no trends were evident.

At harvest, yields in shoot positioned vines were significantly lower in early and double sprayed vines, due to ethephon induced abscission of berries, in shoot positioned vines. Berry weights were significantly heavier in early and double treatments. Corresponding trends in yields, although not significant, occurred in hedged vines. Berries were significantly heavier in all ethephon sprayed vines compared with non-sprayed vines.

Leaf removal significantly increased fruit exposure, resulting in increased anthocyanins and phenols at harvest, although increases were significant in shoot positioned vines only.