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

Root formation problems (3); withered shoot growth (4); vascular tissue problems (5).

PART 5

GRAPEVINE PESTS 5

A s is the case worldwide, the SA wine industry is no exception regarding the incidence of pest phenomena, in which case established vines (above as well as below ground) are continually exposed to attacks – as related to a diverse and wide spectrum of insects and other pests. Abnormalities associated with this in most cases mirror local damage to the relevant organs, with in nearly all cases specifically visible lesions to organ surfaces. Naturally most surface pests are relatively easy to identify, either directly or by abnormality interventions which are induced by feeding actions. In contrast, underground pests are harder to recognise – some because they appear in deep(er) soils and the expression of characteristic abnormalities are less prominent. Although, due to the extensive divergence, the chief focus is on the appearance of the most typical pest-associated abnormalities – which usually occur every year and lead to great crop losses and even contribute to destruction of vines – deliberate efforts have been made to highlight less well-known phenomena where applicable, which may appear sporadically or by exception. Additionally it is of further importance to note that some pests/phenomena may possess both advantageous as well as detrimental traits in terms of viticulture, and that unknown or nearly forgotten and even new pests may attack in sudden and unexpected epidemic proportions. Overall, based on the extensive impact regarding direct and indirect damage which can be exercised by a wide spectrum of pests on affected vines, it therefore remains essential to stay continually informed of identification procedures, as well as typical behaviour and feeding actions. In addition to visual observations regarding the abovemen- tioned actions, as well as times (night or day) when they are exercised, quantity surveys during the months within the growth season in which high population numbers normally occur, are regarded as extremely useful additions regarding suitable identification(s) – in conjunction with typical characteristics of droppings in individual cases.

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