SPRAYING AGAINST THE GRAPE LEAFHOPPER. 9 
a few vines with different dilutions. Accordingly several vines were 
sprayed with the following dilutions: 
Tare 1.—Dilutions of blackleaf tobacco extract as used in experiments against 
the grape leafhopper. 
— 
Bist | ham ae 
ING ber of Strength of dilution. Results. 
* | vines 
103) Aside ealloOni tO. oseallons watelee= <= .\5-22cee-s- a7 Jes | All nymphs hit by spray were killed. 
2 Aq eoalion! toul00jpallons waters s< 2:5. -s--25~.-- sec | Do. 
3 4 1 gallon to 125 gallons water...................-- Do. 
4 4)\i-eallon tom50 gallons water... 2.22. <S2-2-2:.2-.| Do. 
5 45 elcallon to 200 gallons water. --.-2 2.5.5.5 -=-- Do. 
6 4 | Clear water....... Bis cia AR aE So eee | No nymphs killed. 
Blackleaf “40,’' another form of highly concentrated tobacco ex- 
tract, was also used at a much greater dilution, as shown in Table II. 
TABLE II.—Dilutions of blackleaf *‘ 40” as used in experiments against the grape 
leafhopper. 
Num- 
ee ber of Strength of dilution. Results. 
vines. | 
1 4 | 1 gallon to 1,000 gallons water.....-........-.---- All nymphs hit by spray were killed. 
2 4 | 1 gallon to 1,500 gallons water... --. Pee S 5 eee at Do. 
3 4 |-1 gallon to 1,750 gallons water.:.........-.......- Do. 
4 4 | 1 gallon to 2,000 gallons water............-....-.- All but fully developed nymphs were 
killed. 
5 AG R@lCATAWV ALCL as ona ie cee shee oo as ce meees = See | No nymphs were killed. 
All of the spray applications indicated above were made with a 
hand pump carrying a pressure of about 80 pounds. A short rod 
with a nozzle set at right angles attached to a 40-foot hose was used 
to apply the spray to the nymphs upon the underside of the leaves. 
Great care was taken to wet the underside of every leaf. The result 
of these applications could be determined within an hour after they 
were made, or as soon as the leaves became dry. Those nymphs that 
were not hit and killed by the spray would be found running about 
quite actively; thus the efficiency of the spray was quickly apparent. 
It was found that a larger amount and a greater strength of the 
tobacco liquid was required to kill the nearly full-grown nymphs, 
and also that only a very small number of the winged adults was 
destroyed by the spray. 
After the killing strength of the blackleaf tobacco extract had 
been determined, several experiments covering areas of several acres 
each were undertaken in a number of vineyards. On the vineyard 
of Mr. H. H. Harper about 6 acres of the worst infested portion of 
his vineyard was sprayed from July 14 to July 16, when the majority 
of the nymphs were small. Blackleaf tobacco extract was applied 
at a dilution of 1 gallon of the extract to-150 gallons of water. A 
traction sprayer was used and a pressure of from 75 to 125 pounds 
1 Containing 40 per cent of nicotine. 
