General and introductory
For sustainable and profitable cultivation, optimal performance of individual grapevines in the vineyard necessitates a strict adherence to meticulous schedules, from establishment onwards, in respect of the correct application of ongoing and specific practices/actions/techniques. In addition to research-based and strictly scientifically founded guidelines according to which short and long term cultivation practices should be approached and applied, the incidence of abnormality phenomena – as may be associated with unsound/incorrect/negligent execution of specific actions – is by no means unknown, and may still impact on affected grapevines on a sporadic basis. Based on the fact that considerable economic damage/losses may ensue in such instances, it is important here too that applicable, practice-based procedures are implemented in conjunction with expert advice. On the whole it remains important, furthermore, not only to stay abreast of identification procedures vis à vis abnormality phenomena that are thus induced, but also to have a basic knowledge of grapevine morphology and phenology – especially in instances where specific actions are restricted to specific time intervals. In this part of the series details of abnormalities/phenomena resulting from viticultural practices are described and where applicable, visually depicted and elucidated by captions. Due to the wide-ranging extent and highly divergent nature of the phenomena in this category, an attempt has obviously been made to focus mainly on actual characteristic examples.
In all instances where tying material (nylon or plastic rope) is used to limit wind damage during grapevine development, obtain upright trunks, or tie down/keep developing cordon arms in position, it is crucial that correct procedures are strictly adhered to at all times. If such actions have an unsound/incorrect basis, the result can/may be severe choking/strangulation effects – thereby contributing to growth decline or even partial/total dieback in affected grapevines (Photos 503 – 509).
PHOTO 503. Although this example illustrates severe choking/strangulation effects, as a result of tying the rope below instead of above the bud for intended trunk/grapevine development, active scion root development/growth (graft union, as well as choking position covered with soil) may be considered an additional cause of the deteriorating appearance and dieback of this grapevine.
PHOTO 504. Similar to the cause illustrated in Photo 503, severe choking/strangulation is encountered in this Weisser Riesling grapevine. Such situations are reflected where growth and performance are normal in affected grapevines for a certain period, only to be subjected to sudden drying out, especially as a result of stress. PHOTO 505. The reason/cause for the sudden drying out of this grapevine as in Photo 504, is revealed here. PHOTO 506. Early autumn discolouration of leaves resulting from a strangulating effect caused by rope (09:00 position, just left of the fork) on the phloem tissue of the cordon arm in question. Not to be confused with leafroll. PHOTO 507. A typical example of a strangled cordon arm in this Shiraz grapevine. The deeply grooved rope is hard to spot where it is still in position (practically against the fork). PHOTO 508. Due to the possibility of strangulating effects at a later stage, winding of cordon arms around wires during grapevine development is considered extremely unwise. PHOTO 509. An example where the cordon wire has been deeply grooved into the wood and practically covered, in which case possible strangulating effects should not be disregarded. PHOTO 510. A situation where unsound/incorrect winter pruning practices resulted in the grotesque elongation/build-up of bearers/spurs. Also note the strangulating effect (09:00 position) caused on the applicable cordon arm by the deeply grooved rope. PHOTO 511. Although the judicious use of sucker shoots may serve as an effective safeguard against the elongation/build-up of bearers/spurs, timeous action was postponed too long in this example. PHOTO 512. An example where the onset of suckering actions was postponed too long, the result being that the effective removal of undesirable shoots is considerably compromised. PHOTO 513. In this instance the sucker shoots, as in Photo 512, would have been broken, cut or even torn off, thereby favouring the ingress options for wood rotting fungi into numerous wounds. PHOTO 514. Topping machine damage caused to the bunch before véraison. In addition to economic implications, such wounds serve as the ideal points of ingress to rotting organisms. PHOTO 515. Severe leaf and shoot damage caused by the injudicious use of topping machines. PHOTO 516. A typical example of a topping machine ‘ribsteker’, where the shoot was cut off too close above the bunch, the result being that too few effective leaves are retained to achieve normal ripening. PHOTO 517. Considerable damage by topping machines may be caused to mature wood, especially in cases where bearers are not developed/positioned correctly, the result being a tendency to grow sideways. PHOTO 518. Given the wasting of reserves, prompt, timeous and judicious elimination of rootstock suckers, in young plantings especially, is strongly recommended. Also note the favourable conditions for scion root development that have been created in this example – in the sense that the graft union comes into contact with or is even covered by soil. PHOTO 519. Experience has taught that unsound/incorrect actions upon removal of rootstock suckers not only exacerbates the extent of such situations in due course, but progressively compromises measures to permanently curtail the state of affairs. PHOTO 520. The timeous and judicious application of herbicides is considered crucial. Serious toxicity interventions may be caused in exposed grapevines, especially in instances where such actions may be undertaken after clean pruning (fresh pruning wounds), or even during bud swell/emanating of buds. PHOTO 521. Despite successful topgrafting, this example shows a serious lack of ongoing care, as well as timeous grapevine development.
Elongation of bearers/spurs
Based on wide-ranging disadvantages associated with this phenomenon, it remains important that elongation (build-up) of bearers/spurs – which may/can be induced in trained as well as bush vines by unsound/incorrect winter pruning practices – should be restricted to the absolute minimum on an ongoing basis. In this regard a sound knowledge of grapevine morphology, as well as specific pruning methods, is strongly recommended, thereby making provision for ongoing, but especially timeous implementation of specific counter measures (Photos 510 & 511).
Apart from research-based, proven advantages associated with the implementation of sound suckering actions, there are known incidences of abnormality phenomena resulting from situations where scientifically founded guidelines have not been followed satisfactorily. In this regard, it is especially important that the removal of undesirable, young shoots (mainly infertile and water shoots situated in unfavourable positions) should take place during the early part of the growing season, namely when they may be easily rubbed off, thereby avoiding any breaking/tearing or even cutting actions (Photos 512 & 513).
Topping machine damage
In order to prevent damage caused by topping machines, to vigorously growing grapevines especially, it remains crucial for bearer shoots to be tucked into foliage wires timeously, positioned correctly and homogeneous shoot lengths achieved by means of judicious tipping actions. Severe damage may be induced where specific guidelines are not followed – examples exist of situations where: (i) rows were topped too severely to the sides; (ii) effective leaves were excessively damaged/trimmed; (iii) bunches/shoots were damaged; (iv) shoots were cut off too closely above the bunches (‘ribstekers’) and even (v) mature wood was subjected to harmful interventions (Photos 514 – 517).
Despite meticulous preparation of grafting material on a permanent basis, inter alia to prevent the possible emergence of rootstock suckers in nurseries, but especially following vineyard establishment, the sporadic incidence thereof remains a well-known phenomenon. Given the wastage of reserves, which may occur in young plantings in particular (Photo 518), it is strongly recommended that elimination thereof should be prompt, timeous and judicious – including the collar buds on rootstock material from which it is normally derived. Should unsound/incorrect actions be implemented in this regard, experience has taught that the extent of such situations is not only exacerbated in due course, but also that permanent curtailing measures are increasingly compromised (Photo 519).
Based on severe phytotoxic interventions associated with the unsound/incorrect application of herbicides, the meticulous incorporation and application of guidelines based on expert chemical herbicide control strategies cannot be overemphasised. In this regard the priority status of timeous application of chemical products may be singled out in order to prevent, at all costs, the possible uptake(s) through fresh pruning wounds or even swelling/emanating buds in exposed grapevines (Photo 520).
Successful topgrafting of existing grapevines to alternative cultivars is based mainly on: (i) achieving high take percentages with normal and effectively functioning graft unions and (ii) exercising judicious actions to achieve complete grapevine development during the same growing season. Despite guidelines in this regard having been specifically stipulated, it may be expected that – especially in respect of the latter, should either injudiciousness or negligence prevail – that particular season be sacrificed and input that had been remiss be transferred to the following year (Photo 521).
Due to the large-scale extent and high degree of divergence, vis à vis abnormality phenomena that may be associated with unsound/incorrect implementation of short and long term cultivation practices, examples that are representative of the entire spectrum could not be included in a single presentation. Furthermore it goes without saying that the time frame within which specific actions have to be undertaken plays an equally important role. The same applies to the examples that have been omitted. On the whole it may be said, however, that the ongoing, timeous and judicious implementation of specific practices/actions/techniques can be singled out as being crucial to optimal performance of individual grapevines in the vineyard, in conjunction with sustainable and profitable cultivation.
References/additional reading and viewing material
Visser, H., 2013. Tipping and topping guidelines. Wynboer Technical Yearbook 2013, 163 (in WineLand, October 2013).
Winkler, A.J., Cook, A., Kliewer, W.M. & Lider, L., 1974. Training Young Vines. In: General Viticulture. University of California Press, Berkeley and Los Angeles. pp. 272 – 286.
Zeeman, A.S. & Archer, E., 1981. Stokontwikkeling, Wintersnoei en Somerbehandeling. In: Burger, J. & Deist, J. (eds). Wingerdbou in Suid-Afrika. Trio-Rand/SA Litho, N’dabeni. pp. 202 – 233.
Department of Viticulture & Oenology,
For further information contact Piet Goussard at firstname.lastname@example.org.
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