38 BULLETIN 19, U. S. DEPAP.IMEXI OF AGBICULTUBK. 
d on the purple surface of. the ripened grapes, rendering t-hera 
unattractive for table use. 
During :'.: ". .st few years commercial brands of tobacco extracts 
h / me much into use as liquid spray substances for the control 
of soft-l li< sucking insects. Hence once more, after a period of 
over SO years since it was first recommended, tobacco appears to be 
most promising ins (a i "■• : r the control of this pest. 
Doling the seasons of 1910 and 1911 the grape leafhopper was 
i sent in very injurious numbers in many vineyards in the Lake 
Erie Valley. Vineyard experiments were undertaken by the Bureau 
of Entomology in the vicinity of North East. Pa., using the tobacco 
extracts as liquid sprays against the nymphs. The result-, oi these 
experiments were very gratifying, since with one thorough applica- 
tion of the 1 extract the numbers of these insects in the treated 
: . yards were sc j: atly re luced and the injury was so slight that 
the : li ige i -~ lined its dark green color throughout the season, the 
to j: wth " is strong and well matured, the berries were large, the 
fruit sweet, and the size of the crop considerably increased : whereas, 
on the untreated portion of the vineyards the foliage turned brown 
and dro] : -maturely, the cane growth was stunted, the berries 
were undersized and lacking in sug .: ontent, and the tonnage per 
: was much less than on the = ray ::ions of the vineyards. 
Del J] I re] rts of these vineyard experiments against this pest 
are dvei: in Part I of Bulletin No. 97 and Part I of Bulletin Xo. 116 
of this bureau. 
?PRAY MATERIAL. 
The forms of " bac extract used in these experiments in 1 
1911 were the blackleaf tobacco extract containing 2.70 per cent 
nicotine sulphate and the blackleaf tobacco extract containing 40 
per cent of nicotine sulphate. The blackleaf tobacco extract con- 
' lining 2.7 per c ait of nicotine was effective in killing all of the 
nymphs whi h were thoroughly wetted by the spray, when applied 
at a dilution of 1 par: of tobacco extract to 150 parts of water or 
Bordeaux mixture. The blackleaf tobacco extract containing 40 
per cent nicotine sulphate was found to be effective at a dilution 
: ] .r: : :oba xti : to 1.500 parts of water or Bordeaux 
mixture. Both of these forms of tobacco extract appear to be 
equally effective in destroying the nymphs at the dilutions men- 
d. The one containing the smaller percentage of nicotine 
2.7 nt . however, necessarily contains more sticky inert mat- 
ter. When this is applied as . - the vines late in the season, 
i. e.. I the middle of August, and when little rainfall occurs 
re the harvesting season, some of this sticky substance may ad- 
to the ripe grapes, giving the skins a slight flavor of tobacco. 
