302 Report of the Department of Entomology of the 



experimental vineyard. 



Owing to line fences, along which were growing many bushes, 

 besides weeds and grass (Plate IV, figs. 1-3), large numbers of 

 leaf -hoppers went into hibernation during the autumn of 1911 

 along the margins of the vineyard. As these vines are grown for 

 various experimental purposes, all of them were sprayed with 

 nicotine extract to control the insects since it was not desirable 

 to leave checks. However, careful observations were made to note 

 the effects of the treatment on the pest, which showed that the 

 vines were efficiently protected by the spraying. Unfortunately 

 there was in this planting considerable "winter-injury, which 

 caused the vines to appear as if they were damaged by the leaf- 

 hopper, a condition quite prevalent in this region and not gen- 

 erally understood. Thus the vines as a whole did not present 

 the uniform dark green appearance found in most of the other 

 vineyards in which experiments were made. 



relation of leaf-hopper injury to quality of fruit. 



The destruction of leaf tissue by the feeding of these insects 

 causes a decreased wood growth which in time must affect the crop, 

 but by far the most important loss to the grape-growers arises 

 from a depreciation in the quality of the fruit. Concord grapes 

 normally have a bluish-black color when ripened, but fruit from 

 leaf -hopper-infested vines has a red appearance * and a decided 



* In this connection it is important to add a word of caution. The fact 

 that a Concord grape has a red appearance and is poor in quality is not con- 

 clusive evidence that the condition was caused by grape leaf-hopper. A 

 peculiar vine trouble, resembling leaf-hopper injury, was of common occur- 

 rence in the vineyards of Chautauqua county. This trouble can be dis- 

 tinguished from insect injury in several ways: (1) It affects vines which 

 have not been infested with grape leaf- hoppers ; (2) The grape leaf -hopper 

 punctures the epidermis or skin of the leaf and close examination will show 

 distinct yellowish areas uniformly over the leaves caused by the feeding 

 wounds. The ribs of the leaf have a yellow, punctuated appearance. If the 

 leaf dies it will be found to die along the veins as quickly as on the margins. 

 On the other hand vines having " leaf blight" ( ?) show leaves having darkened 

 areas along the veins and the margins yellow and die first. It is important 

 that every vineyardist distinguish between the injuries, for failure to do 

 so has caused the waste of spray materials. 



