THE GBAPE LEAFHOPPEE IN THE LAKE 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; b, labium; c, mandibles; d, max- 
illa; e, maxillary seta. Greatly enlarged. (Origi- 
nal.) 
