GRAPE INSECTS 465 



The Grape Phylloxera 

 Phylloxera vastatrix Plane hon 



This destructive plant-louse is a native of the eastern United 

 States, where it originally infested the leaves and roots of the 

 various species of wild grapes. Sometime before 1863 it was 

 introduced into the great wine-producing regions of France, 

 and there proved a deadly enemy of the European grape {Vitis 

 vinifera). By 1884 a third of the vineyards of France had been 

 destroyed, and a much larger area had been seriously affected. 

 It was introduced into California some time before 1874 and 

 is now present in most of the grape-producing regions of the 

 state except in the southern part. As most of the grapes 

 grown commercially in California are of the vinifera or European 

 type, the phylloxera has there been one of the most important 

 insect pests with which the vineyardists of the Pacific slope 

 have had to contend. The phylloxera has also been introduced 

 into New Zealand and South Africa, and also occurs in southern 

 Russia and in Algeria. 



The life history of the grape phylloxera is a complicated one. 

 In its destructive form it is a small, yellowish, wingless root- 

 louse about yV of an inch in length found clustering on the roots 

 of the vine. In feeding, the louse inserts the sharp and slender 

 stylets of the beak and sucks out the sap, thus causing an 

 irritation which produces an abnormal enlargement of the roots 

 known as nodules. These swellings are yellow in color, soft 

 and watery, and after a time break down and decay, causing 

 the death of the root. The underground forms molt three 

 times before becoming mature ; they are all females and re- 

 produce without being fertihzed. The number of eggs laid 

 by a single individual varies considerably with the cUmate 

 and the season, but rarely exceeds a hundred. The eggs are 

 oval in form, yellow in color and about ^ of an inch in length ; 

 they are laid singly or in clusters on the roots of the vine. 



