34 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE. 
NATURAL CHECKS. 
It would seem, however, that there are some as yet unknown 
natural checks which greatly reduce the numbers of this insect and 
occasionally almost entirely ehminate it over areas where only a short 
time previously it had been a serious pest. 
In 1865 Trimble observed that once when the thermometer reached 
100° F. thousands of the " hoppers" were killed. 
There was a great diminution in numbers of the adults in the 
infested area of the Chautauqua County vineyards early in the season 
of 1903. 
A condition similar to this was observed by Mr. E. W. Scott, of 
the Bureau of Entomology, during the season of 1912, when adults 
of TypMocyba tricincta were so very abundant in the vineyards near 
Benton Harbor, Mich., that the vineyardists became greatly alarmed, 
many of them making preparations to spray the nymphs when they 
should appear. Yet this proved unnecessary, for when the time arrived 
for the nymphs to appear upon the foliage in large numbers most 
of the adults had disappeared and very few nymphs of the new 
brood had hatched. As yet nobody appears to be able to account 
for these sudden disappearances of the pest or to determine whether 
they are due to climatic or other causes. 
In September, 1890, Thaxter observed that in Connecticut grape 
leaf hoppers in large numbers were injuring a vineyard. He found 
that they were attacked by a fungous disease (E?npusa sp.) which 
apparently destroyed all of them. This is the only case on record 
in which this insect was attacked by a fungous disease. Nothing of 
this nature has been observed in the vineyards of the Lake Erie 
Valley during the present investigation, and for the past four or five 
seasons the pest has steadily increased. Probably the time may not 
be far distant when large numbers of them will suddenly disappear, 
as happened at Westfield, N. Y., in the season of 1903. However, it 
is by no means safe for the vineyardist to count on these natural 
checks, for while one is waiting for relief from such a source the pest 
may work incalculable damage- to his vineyard. 
REMEDIES. 
During the period that this insect has attracted the attention of 
economic entomologists much experimental work has been undertaken 
to determine the most effective means for its control. Early in the 
control work undertaken against this pest, tobacco, in some form or 
other, was employed as a killing agent. In 1828 Fessenden (see 
Bibliography) recommended the smoking of infested vines by burning 
tobacco stalks beneath them. 
