﻿TJ4E (JRAPE LEAFHOPPER IN THE I.AKK ERIE VALLEY. 



CHARACTER OF INJURY AND DESTRUCTIVENESS. 



The grape leaf hopper injures the grapevine by attacking the foliage. 

 It is a sucking insect in both the nymphal and adult stages and injures 

 the plant by inserting its threadlike proboscis (fig. 2) into the under- 

 side of the leaf and extracting the juices therefrom. The result of 

 these punctures, and more especially the removal of the juices, is 

 first evidenced by a yellowing or whitening in patches on the upper 

 surface of the leaf (fig. 3), which later turns brown, and finally the 

 leaf falls from the vine prematurely. Where the injury is severe, 

 the whole leaf dries up and becomes almost functionless long before 

 the normal ripening period of the fruit arrives. This arrested func- 

 tioning of the foliage as a result of attack by this pest has a tendency, 

 when the injury is severe, to 

 check the development of the en- 

 tire vine, frequently to such an 

 extent that the cane growth is 

 considerably shortened, the size 

 of the crop of fruit reduced, and 

 the quality rendered inferior by 

 a reduction of its sugar content. 

 During very dry seasons the fruit 

 on heavily infested vines is badly 

 spotted by the droppings of the 

 adult insects. 



The overwintering winged 

 adults commence to attack the 

 new leaves of the vines when the 

 shoots are a few inches in length. 

 Usually the sprouts starting from 

 the base of the vine and the new 

 growth along the lower trellis are 

 the first parts to be attacked. 

 When large numbers of the adults are present feeding on this new 

 growth, patches of yellow soon appear on the upper surface of the 

 infested leaves, and in a short time these injured areas dry down and 

 become brown (fig. 4), and the leaves assume a crumpled appearance, 

 the result being a stunting of the badly infested shoots. During this 

 time shoots higher up on the vine, being less heavily infested, have 

 made a stronger growth which, where the vines are vigorous, soon 

 overshadows the stunted, badly infested shoots along the lower trellis. 

 Consequently it frequently happens that this growth on the lower 

 trellis develops few or no long, normal, healthy canes. 



This condition is of considerable importance, since it is from the 

 healthy, well-ripened canes springing from the lower trellis that the 



Fig. 2. — Head of grape leafhopper, .showing mouth- 

 parts: a, Labrum; 6, labium; c, mandibles; d, max- 

 illae; e, maxillary seta. Greatly enlarged. (Origi- 

 nal.) 



