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

GRAPEVINE PESTS Snout beetles and long-horned grasshoppers 5.2

Snout beetles Snout beetles – the adults have characteristic elongated snouts (with mandibles at the ends) and bulb-shaped, smooth bodies – may be singled out as one of the most important grapevine pests in the local industry (Photos 286, 287 and 288). Eating and feeding actions occur mostly at night (during the day they look for shelter under loose bark sections, in the soil under clods or even in the shade inside bunches) – with the result that serious damage is done to practically all organs above the soil-surface of both rootstocks and scions. The arrival – with accompanying feeding activities – of adults usually takes place from the beginning of October in normal years, and population numbers reach a peak from the end of October to the end of December. Obviously young plantings are extremely sought-after and grapevines can be destroyed during the establishment years – especially in instances where snails, inter alia, target grapevines in conjunction with snout beetles. Characteristic of speckled weevils and/or bud nibblers is an earlier onset (beginning of October), thereby causing serious feeding damage to emerging buds, sprouts and young shoot tips (Photos 289, 290 and 291). In normal years the well-known banded fruit weevil/grapevine snout beetle arrives on the scene from the end of October onwards and eats characteristic clear-cut holes without stringy filaments in leaves (the edges of which turn brown quickly) – as well as half-moon shaped indentations at the edges. In serious instances leaves are quickly turned into a sieve-like format, which may contribute to overall drying out (Photos 292 and 293). In addition, shoots are eaten to such an extent that obvious spots or holes are visible on the surface – in some instances this contributes to the snapping of shoots (Photos 294 and 295). Damage to the bunch is usually associated with characteristic feeding patterns on peduncles and parts of the bunch, pedicels and even berries (Photos 296, 297 and 298). Such feeding damage may furthermore give rise to berries drying out and dropping off (Photo 299) – sometimes bunches even wilt completely. In instances where the involvement/incidence of snout beetles is suspected, nocturnal visits are highly recommended – in which case feeding activities can be observed very effectively using a source of light (torch) for reliable identification procedures. Although several snout beetle species occur on grapevines, the above-mentioned examples are most representative of damage caused by the well-known banded fruit weevil; as well as the bud nubbler and speckled weevil. Long-horned grasshoppers Although feeding damage by long-horned grasshoppers is mostly not considered to be of great economic importance, the contrary is proven by sporadic outbreaks of large numbers (here climatic conditions play a decisive role), especially in cases where even young bunches, in addition to leaves, are subjected to active feeding actions. Unlike snout beetles, long- horned grasshoppers are also active during the day and reliable identification – based

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