The grapevine and its fruit are seriously attacked by a number of insects and diseases. Diseases cause more damage than pests, particularly in the more humid regions.
Two of the more important insect pests are the grape berry moth and la cochylis. Both are well known in Europe, and also occur in Egypt, North Africa and Japan. Damage is caused by the caterpillars feeding on the developing fruit. In the USA the grape leaf-hopper is the most important pest. The Vine phylloxera, a type of aphid, occurs in most vine-growing parts of the world, in Europe, North Africa, South Africa, South America, Australia, Mexico and the Middle East. The insect appears to have been introduced into Europe from America about 1860. In California it caused devastation in the vineyards, and in France it destroyed at least 1,500,000 hectares and threatened the total extinction of the industry.
Of the numerous diseases that attack vines, two fungal diseases are of outstanding importance: vine downy mildew and powdery mildew. Both are natives of the USA. Vine powdery mildew, which lives on both the leaves and fruit, crossed the Atlantic in 1845 (the same year as potato blight) when it was first recognized in England. It reached France in 1848 and then spread steadily through Europe. It is now found wherever grapes are grown. Vine downy mildew reached France in 1878 on rootstock imported from America because of its aphid resistant qualities (the destructive aphid, Phylloxera, had also been introduced from North America) and soon reached epidemic proportions. The disease is of particular importance in the more humid regions such as France, Italy and parts of Spain, but negligible in the drier climates of California. The most important vine disease in the USA is black rot; it is estimated to cause losses of about 20% in the south, and up to 10% in the north.