Virus diseases of grapevines in New Zealand

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Abstract
Field surveys of vineyards in the major vine-growing districts indicate that grapevine fanleaf and leafroll viruses are widespread and of high incidence in New Zealand, and that enation disease, which is possibly caused by a strain of fanleaf virus, and yellow mosaic, a strain of fanleaf virus, are present but of low incidence. Field diagnoses of fanleaf and leafroll viruses have been confirmed by transmission to indicator varieties. Symptoms of fanleaf and leafroll viruses are the same as those described for these two viruses in other countries, but, except in a few varieties, fanleaf symptoms are not very pronounced under New Zealand conditions. All vines of many popular varieties appear to be infected with one or both viruses. The many grapevine introductions made since the first vines were brought to New Zealand in 1819 have provided ample opportunities for the introduction of virus diseases. It is unlikely that grapevine viruses spread naturally in New Zealand, for natural spread of leafroll virus is not known to occur, and Xiphenema index, the only known vector of fan leaf, has not been found in this country. However, the practice of grafting over old vines to new or better varieties and the taking of cuttings of Phylloxera-resistant rootstocks from grafted vines on which the scions have failed could explain why virus diseases have become so widespread throughout our vineyards.

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