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

GRAPEVINE PESTS Mealybug and ants 5.3

Incidence, spread and damage During winter, affected grapevines are mostly associated with black, sooty mould covered trunks/cordons and during early spring, the incidence of mealybug can already be exposed through bark removal – especially in cases where ants may already be active. In contrast with readily identifiable adult females – whose oval-shaped bodies are richly endowed with white, powdery wax secretions and short fringe-like protrusions – young larvae are more difficult to observe, especially in situations where their presence is already widespread. During the larval stages – in which case numbers are rapidly augmented, on an ongoing basis, by actively functioning adult females – mealybugs are very mobile and migrate quickly, taking possession of shoots, leaves, bunches and even roots. Feeding requirements are satisfied by sucking out plant sap, at which time large amounts of honeydew are secreted – to be utilised respectively by ants (as a sought-after source of food) and sooty mould fungi (as ideal growth medium). In this presentation particulars about abnormalities/damage related to the incidence and spread of mealybug on affected grapevines are visually portrayed and elucidated in the most appropriate way by succinct, though basic captions (Photos 307 - 323).

198 • A Guide to Grapevine Abnormalities in South Africa