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

Pre-emergence herbicide phytotoxicity.

(2,4-D) or even 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). Depending on the intensity levels of uptake, serious damage may be inflicted on applicable organs, to the extent that grapevines may die back entirely (Photos 489 - 494). Glyphosate As in the case of phenoxyacetic acid, glyphosate induced phytotoxicity is also associated with application on fresh pruning wounds, either during bud swell/emanation of buds, or when spray-drift comes into contact with green shoots and grapevine leaves especially. Although phytotoxicity normally displays characteristic, visually detectable traits, these are often widely divergent and it is therefore recommended that expert advice be sought in confirmation. In addition, toxicity phenomena often lead to confusion with other and even totally divergent causes, which may further complicate positive identification. Based on the intensity levels of uptake, here too, serious damage may be inflicted on applicable organs, to the extent that grapevines may even die back entirely (Photos 495 - 502).

PHOTO 481. Although widely divergent, interveinal yellowing/browning from leaf edges is considered characteristic of root uptake of pre-emergence herbicides (where triazines are the active ingredients).

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