THE GRAPE LEAFHOPPER IX THE LAKE ERIE VALLEY. 41 
cess with any type of spray apparatus in present use in work against 
this pest appears to depend more on the care and ingenuity of the 
individual operator than upon the great superiority of any given type 
of machine over another. 
RECOMMENDATIONS. 
Efforts to control the depredations of the grape leafhopper by the 
destruction of the winged adults, by burning over or cleaning up 
their hibernating places adjacent to vineyards, by trapping them on 
sticky shields, or by endeavoring to treat them with contact sprays 
when they appear on the new growth of the grapevines in spring 
before oviposition takes place, have proven far from satisfactory. 
Although these methods may furnish a certain measure of relief over 
very limited areas, they are of very slight practical value as control 
measures when serious infestations occur in large vineyards. 
Observations indicate that except in seasons of extremely heavy 
infestation, or over limited areas, the injury wrought by the over- 
wintering adults in spring to the new growth is not likely to reduce 
greatly the entire seasonal growth of the infested grapevine provided 
a large percentage of their offspring in the form of nymphs can be 
destroyed before they reach the adult stage. In other words, it is 
the steady drain made on the infested grapevines from the time the 
overwintering adults attack them in spring, combined with the 
unchecked attack of the nymphs and adults of the new brood until 
late September, that results in serious injury by curtailing the size of 
the crop and the growth of the vine. 
That the nymphs can be controlled by the spray method has been 
thoroughly demonstrated. Successful control of the nymphs by this 
method depends on thoroughly wetting all parts of the underside of 
the infested leaves with the spray liquid. 
Tobacco extracts have given excellent results, used according to 
the following formulas : 
I. Tobacco extract containing 2. 70 per cent nicotine sulphate, diluted at the ratio of 
1 part to 150 parts of water. 
II. Tobacco extract containing 40 per cent nicotine sulphate, diluted at the ratio of 
1 part to 1.500 parts of water. 
The killing quality of the tobacco extract is apparently just as 
effective when added at the same dilution to the Bordeaux mixture 
and arsenate of lead spray liquids, which are used to control fungous 
diseases and chewing insect enemies of the grapevine, as when used 
with clear water. No injury results from combining these spray 
mixtures, namely, tobacco extract, Bordeaux mixture, and arsenate 
of lead. However, the tobacco extract should not be mixed with 
spray mixtures containing arsenicals in the form of Paris green or 
arsenite of lime, for serious injury to the foliage is likely to occur as 
a result of the combination. 
