16 Farmers’ Bulletin 1220. 
together on the leaves continuously until the approach of cold 
weather, when the adults seek suitable hibernation quarters as 
described. 
CONTROL. 
Extensive tests of sprays by the Bureau of Entomology and others 
in the East have shown conclusively that the grape leafhopper can 
be controlled by a single application of a spray of dilute nicotine, 
such as nicotine sulphate containing 40 per cent nicotine. The nico- 
tine sulphate is used at the rate of approximately one-fourth pint 
to each 50 gallons of spray, and in general it may be added to the 
Bordeaux mixture and arsenate of lead spray, employed for the treat- 
ment of other grape insects and diseases, as described in the spraying 
schedule (p. 74). Where the leafhopper is especially troublesome 
Fig. 14.—Grape leafhopper. Cast skins of nymphs on undersurface 
of grape leaf. 
it should be promptly treated when the nymphs are in the proper 
stage of growth (see fig. 12, c), even if an extra treatment is neces- 
sary. It is essential to direct the spray against the nymphs on the 
lower surface of the leaves, and fairly coarse nozzle disks should be 
used, as a fine mist spray does not wet the insects sufficiently to Ill 
them. The so-called trailer method (p. 72) of spraying has been 
found best to secure effective results, though in fairly level vine- 
yards a system of nozzles mounted on swinging booms, developed 
by the Geneva, N. Y., Agricultural Experiment Station, has been 
employed with success. When treating only this insect, as may often 
be the case in California, the nicotine sulphate may be used in water, 
but there should be added rosin fish-oil soap, at the rate of 1 pound 
to 50 gallons of water, to improve the spreading and adhesive quali- 
ties of the liquid, 
