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A Technical Guide for Wine Producers
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RECENT ARTICLES | WYNBOER HOME
GROWTH
TUBES FOR ESTABLISHMENT OF VINEYARDS Introduction A large percentage of the vineyards in South Africa still
develop unevenly during the first year of establishment. Consequently all
the vines cannot be developed on the cordon wires in the same year and the
vines have to be pruned back either to "kierie" or two bud stages. Various growth tubes have appeared on the South African
viticultural scene over the past two years. Most of these tubes were
initially developed to improve the growth of young trees in the forestry
industry. Growth tubes have been used in countries such as the United
States (California), Australia and in parts of Europe for many years to
promote uniform development of the vine in newly established vineyards
from the first year of establishment. Scientific results from abroad have
already indicated that the use of these growth tubes not only promotes
overall vine development, but also entails large financial advantages for
the producer in that the vines come into production at an earlier stage
and vineyard management inputs are reduced (reduced irrigation
requirements, better weed control in young vineyards, etc.) (Boyer, 1982;
Due, 1996; Treeshelters, 1997). Although these growth tubes have been used
by South African producers for the past two years, the influence thereof
has not been evaluated in a scientific manner for South African
conditions. Material and methods
Ten different growth tubes were installed on 8 and 9
October 1998 during budding in a newly established Chardonnay vineyard in
Robertson (Photo 1), and just after budding in a Sauvignon blanc vineyard
at Nietvoorbij (Photo 2). A control, where no tubes were installed, was
also included at each of the sites. The two trials were laid out according
to a randomised block design with five repetitions of 10 vines per site.
In Robertson irrigation was applied using micro-spitters according to
class A pan evaporation figures. The vineyard at Nietvoorbij received
three additional irrigations by means of sprinkle irrigation. In Robertson
temperature sensors were installed inside and outside the growth tubes to
monitor inside and outside temperatures on an hourly basis.
During the evaluation of the tubes the following aspects
were monitored:
One of the most important requirements during
installation and afterwards is that the base of the tubes has to be sealed
with soil on the outside to a height of at least 5 cm or sunken to a depth
of 5 cm to eliminate air flow from the bottom. The soil at the base of the
tube must be compacted by treading on it, in order to seal the tubes
properly at the base.
Results and discussion
The results of nine of the growth tubes are reported
below. A general overview of the first year's results is given and no
recommendations are made regarding results obtained with specific tubes. A
few advantages and disadvantages of the tubes will be discussed.
Advantages of growth tubes
Disadvantages of growth tubes
Vineyard performance
Growth tempo was monitored on a
weekly basis and the main shoot was topped at cordon wire height as soon
as it reached pencil thickness. The first suckering took place at the
beginning of December 1998, when most shoots started growing out of the
top of the tubes. This was followed by a late suckering at the beginning
of February 1999.
Table 1. The influence of growth tubes on the average
shoot length of Chardonnay and Sauvignon blanc as measured during the
topping of vines at pencil thickness.
All the growth tubes improved the growth rate, making the
vines grow faster (Fig. 1 & 2 ). The effect was more prominent in the
warmer Robertson area where the shoot length increased to approximately
three times the tempo of the control. In general it seems that some of the
tubes caused the vines to develop faster than others, but when considering
the number of days taken by the vines to reach topping thickness, it is
clear that the shoot thickness of the vines did not develop at the same
tempo and the difference between vines in the tubes (tube vines) and the
control vines was not so prominent (Fig. 3 & 4 ). At Nietvoorbij some of the tube vines reached topping thickness up to 24 days before the
control and in Robertson up to 44 days earlier. Although the difference in
performance between individual growth tubes in Robertson was significant,
on average none of the manufacturers' tubes performed better than the
others.
Table 1 shows the average shoot
length at which the various tubes' shoots reached topping thickness.
Although there were a number of significant differences, the information
on its own is not worth much. The average number of days the vines took to
reach topping thickness indicates that the tempo of shoot thickening does
not differ between vines.
Table 2. Damage noted
on Sauvignon blanc (Nietvoorbij) and Chardonnay (Robertson) vines that
developed in growth tubes.
0 0 5 0 0 0 2.5 0 2.5 0 2.5 0 0 0 2.5 0 2.5 0 0 0 5 0 7.5 0 0 2.5 0 0 0 0 0 0 7.5 7.5 12.5 0 2.5 0 2.5 5 0 0 . 0 . 7.5 . 0 0 0 0 5 0 0 0 0 0 0 0 0 During the period of tube evaluation, any damage that occurred was noted (Table 2). The heat damage occurred at an early stage and was caused largely by tubes that had been blown over. In one instance at Nietvoorbij one tube blew away on an extremely hot day and although another tube was installed the same day, the vine died. Otherwise there was no heat damage of either leaves or stems. A few growing tips turned downwards inside the tubes when the tendrils attached themselves to the growing tips and prevented the tips from growing upwards. At Nietvoorbij in particular strong winds blew off a few growing tips above the tubes. Although snails and snout beetles occurred at an early stage, they were effectively controlled by the usual means. The only other pest observed was damage by the big green vineyard caterpillar, but this was only in March and did not last long. While no downy mildew, powdery mildew or any other diseases occurred on the vines in the tubes, they did affect the control. However, downy mildew developed on the leaves as soon as they grew out of the tubes and was curbed by the usual spraying. Temperature data recorded in Robertson from the beginning of October to the end of March 1999 indicated that the temperature inside some of the tubes rose as high as 51.5 C. During the coldest period of evaluation, November 1998, the temperature inside the tubes dropped to as low as 2.1 C. A few of the coldest and warmest days are indicated in Figures 5 and 6. During the coldest period the temperatures inside all the tubes were higher than at the control on the corresponding height and also higher than the average maximum day temperatures measured at the local weather station. At the coldest time of these days it was also lower than that of the outside temperature and average minimum daily temperature. The same trend also occurred during the warmest period, but more prominently at the warmest and coldest times of the day. The reasons for the lower temperatures inside the tubes are firstly the lack of wind movement and secondly the high humidity inside the tubes. This confirms the manufacturers' warning that growth tubes offer no protection against frost. Stem circumferences measured when the tubes were removed in April 1999 indicated that growth tubes at Nietvoorbij did not increase the stem thickness of Sauvignon blanc, but that the stems were in actual fact slightly thinner (Table 3). In Robertson the growth tubes did indeed improve the stem thickness of Chardonnay. Although the difference may be a cultivar effect, it appears that the warmer climate may be more beneficial for the use of growth tubes. According to Dr Mark Potter of Tubex these results conform to their findings. According to their researchers the xylem vessels of the growth tube vines appear to be bigger than those of non-growth tube vines. The bigger vessels are more beneficial with regard to the translocation of nutrients in the plant. According to these researchers a possible explanation for the thinner stems of growth tube vines in cooler conditions may be that stem thickness does not increase much since the vines are isolated from any wind movement which usually blows them around and improves cambium thickening. Table 3. The effect of growth tubes on the stem thickness of vines during the first year of establishment of Sauvignon blanc at Nietvoorbij and Chardonnay in Robertson.
Growth tubes have another positive
effect and possibly also a financial advantage in that as much as 87.5% of
the cordons of growth tube vines in Robertson, as opposed to 28.9% of the
control vines' cordons, were already fully developed on the cordon wire
after the first season. At Nietvoorbij, which is cooler and with Sauvignon
blanc being a more vigorous grower than Chardonnay, this was not the case
however. Conclusions and recommendations The use of all three manufacturers' growth tubes boosts the development of vines in both the cooler Stellenbosch and warm Robertson areas due to the mini-hothouse conditions that are created (Photos 7 & 8). Vines reach topping thickness at the cordon wire earlier and cordons may be developed more quickly in the warmer area. Based on the first year's results growth tubes can be recommended, but it should be remembered that the tubes must be applied correctly and that vines should not be stripped of all their leaves during suckering. A final recommendation will be made at the end of the second year of the investigation.
Acknowledgements The technical assistance of the staff at ARC-Nietvoorbij and Robertson Experimental Farm is much appreciated. Thanks also to the staff at ARC-Nietvoorbij Disease Control Section for monitoring the occurrence and control of pests and diseases. Literature BOYER, J.S., 1982. In general crops are limited to about 25% of their potential yield by the impacts of environmental stress. Plant productivity and environment. Science 218: 443-448. DUE, G ., 1996. Success with vine shelters. Winegrowing 39-45. T REESHELTERS, 1997. Growth tube experiences. Seven growers share secrets of success. Grapegrowing 33-40.
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Three
manufacturers/ distributors of growth
tubes, namely Treessentials, Tubex and Viticor/ Global Green
approached ARC-Nietvoorbij in 1998 to evaluate their respective growth
tubes, namely Super Tubes, Tubex and Snapmax. If the growth tubes do
indeed entail the advantages that have been proposed, it will be to the
producer's financial advantage because vineyards will not only come into
production at an earlier stage, but the economic breakeven point may be
reached a year or more sooner. With a plant width of 1m x 2.75m (3 636
vines/ha), at present the initial capital outlay for the purchase of these
growth tubes can amount to between R12 726/ha and R10 200/ha, which is
relatively high. An advantage of these tubes is, however, that they may be
used repeatedly and have a guaranteed life expentancy of 3 to 5 years. At
the present cost this means an expense of only R2 545.20/ha or 70
cents/vine. If the production claim of 17.23 t/ha to 22.22 t/ha for
Chardonnay may be reached in the second year after establishment (Boyer,
1982), it means that the total cost of the growth tubes will already be
recovered in the first two years.
User friendliness during installation, after
installation and during the removal of the tubes.
All tubes already have the required holes and/or
clips to attach them to cordon wires or wooden poles, reeds, etc. Here
it is important to note that the tubes have to be securely attached to
cordon wires or irrigation wires so that they will not move and blow
away during strong winds. Some of the tubes are equipped with specially
designed snap locks to attach them to the cordon wire and prevent them
from moving on the cordon wire (Photo 3). 
The temperature and humidity inside the tubes are too
high for the development of downy mildew and powdery mildew. Spraying
against fungal diseases is therefore unnecessary until the shoots start
to extend out of the top of the tubes and spraying costs are thus
reduced. 
Some of the tubes first have to be folded or stapled
before they can be installed. This may take up to 11 or 12 seconds per
tube. When the tubes are stapled, one should ensure that the sides do
not overlap too much, otherwise the volume of the tube is reduced and
the efficiency of the tube may be restricted. This often results in
shoots growing out of the sides of the tubes. This also happens when the
tubes are not properly clipped shut or stapled (Photos 5 & 6).
Snapping the tubes open and shut or removing them
during suckering may be time consuming. 
Just a single warning, please note that the tubes must be
removed on a cool day in April. If they are removed before then, the stems
may scorch, and if they are removed at a later stage, the stem's wood will
not ripen properly before winter.
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