A Guide to Grapevine Abnormalities in South Africa - P.G. GOUSSARD

Choking/strangulation effects 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). 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). Suckering 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).

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