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31/10/2014

Mechanical pruning: it seemed a good idea at the time

By Richard Smart

Richard Smart raises concern that the practice of mechanically hedging vines is contributing to trunk disease infections.

Introduction

This title will cause many colleagues to scratch their heads and wonder if Richard Smart has finally lost the plot. Who could possibly question if this technological advance, now widely used in Australia, and for more than 30 years, is appropriate?

Why might mechanical pruning not be appropriate for Australian vineyards in 2014? I can think of two reasons for this proposition. First, and perhaps most significantly, vineyard production might not be sustainable under mechanical pruning, due to impacts on vine health. I discuss this subsequently.

Secondly, mechanising pruning is a further step down the slippery slope of having cost-cutting as the primary goal of viticultural practice. ‘Quality be damned, we must produce grapes more cheaply’ was and still is the catch cry. I wrote an article entitled ‘Has the mantra of cost-cutting contributed to the present problems of the wine sector’, published in the Australian and New Zealand Wine Industry Journal, predecessor to this journal, in the January/February 2010 issue. Cost-cutting can be justified for a bulk wine industry, but not for fine wines. Is this where Australia is headed? Sadly, present statistics suggest an affirmative answer.

Historical background

The late 1960s and the early 1970s were periods of change in the Australian wine sector. This was a period of growth, especially for corporate investment, and notably in the southeast of South Australia, around Padthaway and Coonawarra.

The development of these large vineyards put strain on local resources, especially labour. By this time the mechanisation of harvest was quite well progressed.

Also the entrance of corporate accounting to the wine sector caused scrutiny of vineyard costs, and the high labour costs of pruning were conspicuous. It is no surprise to learn that the possibility of mechanising pruning was considered.

Experiments in eastern United States

The idea of mechanical pruning of grapevines was not new. Professors Nelson Shaulis (viticulture) and Stan Shepherd (engineer) of Cornell/Geneva and associates had been experimenting with mechanical pruning since 1956. They had already demonstrated that dense canopies trained to a single curtain promoted shade, and that yield and fruit composition could be improved by canopy division to eliminate shade, i.e., the Geneva Double Curtain.

Experiments conducted in 1971 and 1972 questioned which was the best way to achieve good yields by mechanical pruning with cutter bars. The answer was clear, using a high cordon and pruning to medium length (seven to 10 nodes) and downward pointing canes. Intrieri, in Italy, was to find the same result many years later. A rotating, stiff wire brush was used in New York for shoot removal along the cordon, which helped avoid shade. Interestingly, as well as developing the world’s first mechanical pruner, mechanical shoot positioners and harvesters were also developed by this enterprising team.

Australian experience

Mildura grower Bob Hollick was an early pioneer of mechanical pruning in Australia, using cutter bars. All of the early effort was about mechanising spur pruning and one of the first casualties was the loss of control of bud number at pruning. Initially some used a ‘hand follow-up’, but this was found generally unnecessary.

During the late 1970s, I worked at Roseworthy Agricultural College with Associate Professor Peter Dry. The college was granted research funds to study mechanical pruning by the Australian Wine Board. Workshops were held at the college in 1977 and 1979. The workshop in 1979 reviewed commercial experience to date throughout Australia, and also experimental data from Roseworthy, Nuriootpa, Loxton, Griffith and CSIRO Merbein.

By this time, circular saws mounted on a variety of platforms were being used, as well as cutter bars.

The full article appears in the September-October 2014 issue of the Wine & Viticulture Journal. To ensure your copy, visit www.winebiz.com.au/wvj/subscribe/

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