﻿4 BULLETIN" 19, U. S. DEPARTMENT OP AGRICULTURE. 



hibernate, the low-growing foliage of underbrush and shrubs will 

 have nearly all of the green coloring matter extracted by this pest 

 and present a whitened or sometimes brown appearance before the 

 spring migration of the insect takes place. Those adults which winter 

 in the vineyards feed upon the green blades and leaves of grasses, 

 weeds, and the various plants that are grown as cover crops. When 

 the leaves of the cultivated grapevine commence to unfold there is a 

 wholesale migration from the foliage of the wild plants, and even 

 from the foliage of wild grapevines, to that of the cultivated vines, 

 amounting in the course of a week or so, from about May 10 to 25 in the 

 region of the Lake Erie Valley, to a complete desertion of the foliage 

 of all plants other than those of the wild varieties of grape and possibly 

 the Virginia creeper. The percentage of hibernating adults remaining 

 on the wild grapevines is very small compared with the number found 

 there before the spring migration to the vineyards has taken place. 



It has been observed that in seasons when the infestation through- 

 out the vineyard area of the Lake Erie Valley has been light, some 

 of the thinner-leaved varieties, such as Delaware and Brighton, are 

 apparently more heavily infested and suffer more from the attacks 

 of this pest than do the thicker-leaved varieties, such as Concord and 

 Niagara. On the other hand, when these insects are very numerous 

 throughout a large vineyard area but little if any difference in 

 respect to the amount of injury to the different varieties can be 

 observed. Usually vines of weak-growing varieties suffer most from 

 attack by this pest, yet it has been observed, in run-down Concord 

 vineyards in which the foliage was sparse, that reproduction of the 

 leafhopper during the summer of 1912 was not so great on such 

 vines, even where the overwintering adults were very numerous in 

 spring, as in adjacent vineyards where vines of the same variety 

 were more vigorous and the foliage was more dense. 



Although many observations have been made to determine if this 

 insect reproduces on the foliage of plants other than the wild and the 

 cultivated grape, all the evidence secured has been of a negative 

 nature. Attempts were made to rear nymphs on the foliage of the rasp- 

 berry, which appears to be a favorite food plant of adults when they 

 leave hibernating quarters in the spring. A large number of adults 

 were confined in Riley cages containing raspberry plants. Although 

 much of the foliage was whitened as a result of their feeding and many 

 of the adults lived until about the middle of July, there was no 

 appearance of nymphs at any time during the season upon the foliage 

 of these plants. All observations during this investigation indicate 

 that this insect reproduces only on the foliage of the wild and cul- 

 tivated grapes, and that where vines of cultivated varieties are avail- 

 able it shows a preference for them and reproduces more freely upon 

 them than upon the wild species. 



