WINETECH Technical Yearbook 2020

Trellis systems in Worcester and Breedekloof

INTRODUCTION This article focuses on trellis systems that are currently being used for new vineyard plantings in the Worcester and Breedekloof areas, and new trends that have emerged the past 10 years. The trellising of vineyards can be defined as the use of supporting structures, usually poles and wire, to accommodate the climbing growth habit of the grapevine in such a way as to ensure effective utilisation of all resources. There are many factors that influence the choice of trellis system, like the soil potential, climate and moisture supply, cultivar and rootstock choice, cost of the system, as well as the expected wine objective. In particular it is the cost, wine objective and ultimately the expected income per hectare that are currently playing a determining role in the decision- making process of choosing a suitable trellis system for these two regions. VINEYARD SURFACE According to the latest SAWIS statistics (2018), the vineyard surface is as follows: Wine grape cultivars in SA wine industry: 93 021 hectares Wine grape cultivars in Worcester: 6 505 hectares Wine grape cultivars in Breedekloof: 12 604 hectares

THE TWO MOST IMPORTANT TYPES OF TRELLIS SYSTEMS IN WORCESTER AND BREEDEKLOOF For the purposes of this investigation, all the different hedge and Perold systems used in Worcester and Breedekloof, are listed separately in table 1. For discussion purposes, all hedge as well as Perold systems are grouped together collectively. THE PEROLD SYSTEM All the Perold trellis systems involve the use of one or more sets of permanent, parallel canopy wires between which the shoots grow (figure 3). The three-strand Perold trellis system is probably still the most widely used system in the South African wine industry. It basically consists of a cordon wire with two parallel wires, 25-30 cm higher. These canopy wires can be moveable, to make it easier to tuck shoots between the wires, or in a permanent position. There are several variations of vineyard trellis systems and those being used in Worcester and Breedekloof are indicated in table 1. The disadvantage of the Perold system is that the tucking/pushing in of shoots can lead to a dense canopy. This causes yellowing of the leaves, poor colour in the case of red grapes, and can also lead to bud infertility. To ensure quality, management practices like suckering, leaf removal and crop control are critically important. Over the past 10 years, 3 295.44 hectares (46%) of vineyards have been trellised using one of these systems.

JULY 2020

PIERRE SNYMAN: Vinpro, Worcester KEYWORDS: Trellis systems, vineyard management

WINETECH TECHNICAL YEARBOOK 2020 137