DeSales hb Bul Ot (Part 1: D. F. I. I., Issued March 31, 1911. 
PAPERS ON DECIDUOUS FRUIT INSECTS AND INSECTICIDES 
SPRAYING EXPERIMENTS AGAINST THE GRAPE LEAF- 
HOPPER IN THE LAKE ERIE VALLEY. 
By FRED JOHNSON, 
Agent and Expert, 
INTRODUCTION. 
The grape leafhopper (7yphlocyba comes Say) (fig. 1) is an enemy 
of grapevines familiar to almost every vineyardist, and doubtless at 
times it has hecome so-numerous and destructive in his vineyard as 
to cause him considerable anxiety. Usually, however, in the vine- 
yards of the Lake Erie Valley, serious dep- 
redations by this pest are confined to some- 
what limited areas adjacent to rough lands 
and woodlots. A few vines at the ends of 
the rows or a few rows along the outside of 
vineyards will be injured year after year 
until the crop yield on these vines is consid- 
erably reduced. Under these conditions it 
receives slight attention from the average 
vineyardist and is regarded as more or less 
of a negligible quantity. Periodically, how- 
ever, some as yet unknown conditions seem 
to favor its multiplication and it spreads 
over wide areas causing injury amounting 
to many thousands of dollars. Such a con- 
dition obtained in the vineyards of Chautau- 
qua County, in the vicinity of Westfield, 
N. Y., during the seasons of 1901 and 
1902, when many hundreds of acres of 
Fic. 1.—The grape leafhopper 
(Typhlocyba comes var. colo- 
radensis) : Adult. Greatly 
enlarged. Original.) 
vineyards suffered greatly from the injury wrought by this pest. 
In 1903 the insect disappeared to a considerable extent and serious 
injury was again confined to limited areas until the season of 1910. 
The insect is now manifestly on the increase and during the past 
season (1910) spread through large blocks of vineyard. In fact, 
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