quarantine of imported plant material plays an important part in international viticulture, and can put a (necessary) brake on certain aspects of its development. Like any form of agricultural quarantine, it can annoy travellers but is designed to protect farmers from the ravages which may be caused by the introduction of pests and diseases from other countries or regions (see the history of downy mildew, powdery mildew, and phylloxera). Most of the devastating pests and diseases of the vine species used commonly for wine production, vinifera, have in fact been spread from America, american vine species having developed a tolerance to these diseases which the European V. vinifera lacks.
