New York Agricultural Experiment Station. 817 



perennial plants, preferring the foliage of bush fruits. As soon 

 as the grape leaves appear they migrate to the vines and feed on 

 them until fall. Thej will be noticed first on shoots and leaves 

 near the ground, but later on all parts of the plants. 



They mate during the latter part of May and the eggs are laid 

 during the month of June. The first nymphs appear about the 

 middle of June and the maximum number is out by the end of 

 the first week in July in normal seasons. A second partial or 

 complete brood appears the latter part of August if conditions are 

 favorable. By the time the grape leaves have fallen most of the 

 insects are mature and seek protected hibernating places. 



The grape leaf-hopper feeds by sucking, and, pre- 



How the ferably, on the under side of the leaves. It pierces 

 hoppers the " skin " of the leaf, feeds until satisfied and 

 work. then withdraws its proboscis or sucking tube thus 

 leaving an opening from which the plant juices 

 dry out, not only from the pierced cell, but from adjoining ones. 

 There is soon formed around each puncture a spot of dead tissue ; 

 and if there be 100 hoppers on a leaf, each feeding twice a day for 

 two months, the leaf would show 12,000 such injured spots. In 

 fact, counts have been made on leaves of average size that gave 

 20,000 spots. This makes a severe drain on the vitality of the 

 leaf and it takes on an unhealthy yellow hue. The death of so 

 many starch-making cells lessens the amount of wood produced 

 and of fruit formed; and, more disastrously perhaps, it aifects 

 the quality of the fruit, making it ill flavored or sour and poorly 

 colored. The rich blue black of the Concord becomes a lifeless 

 reddish color when hoppers are abundant and the attractive flavor 

 is lost so that grape juice makers and most buyers of grapes for the 

 table reject the fruit. 



As the leaf-hoppers feed by sucking, they cannot 

 Control be poisoned ; but must be killed by contact insecti- 



measures. cides. In tests made during 1910, it was found 



that the nicotine preparations were very effective 



if properly applied. But the protection given by the manner of 



feeding beneath the leaves made it almost impossible to reach 



