12 DECIDUOUS FRUIT INSECTS AND INSECTICIDES. 
Mottier on August 3. At this date many of the nymphs had devel- 
oped to adults and these were very active. 
The blackleaf tobacco extract was used at a strength of 1 gallon 
to 100 gallons of water and applied in the same manner as in the 
previous experiments. Evidence of injury, namely, the yellowing 
of the infested foliage, was already noticeable. Shortly after the 
application was made, however, it was observed that the yellowing 
and browning of the foliage ceased on the sprayed: portion, whereas 
on the untreated portion of the vineyard it increased, and by the end 
of September the difference in color and vigor of the foliage on the 
two blocks was very marked, although not so much so as in the 
blocks that were sprayed about the middle of July before any of the 
nymphs had attained full growth and developed wings. This indi-. 
cates that the best results can be obtained by treating the nymphs 
before they commence to make too heavy a drain on the vines. An 
additional reason why the earlier application of the tobacco extract 
is desirable is that if it is applied earlier in the season, when the 
nymphs are small, a weaker dilution may be used. There are thus 
several advantages for the earlier application: First, the cost of the 
material is reduced; second, the drain on the foliage wrought by 
the large numbers of nymphs is checked; and, third, the possibility of 
tainting the berries of the fruit with the taste of tobacco—a condi- 
tion that was slightly noticeable upon the fruit in the vineyard which 
received the latest treatment of the season—is avoided. 
CONCLUSION. 
For several years past injury by the grape leafhopper in the vine- 
yards of the Lake Erie Valley has been confined to limited areas. 
Its increase and dissemination during the season of 1910, however, 
should be a warning to the vineyardist to be prepared to combat it 
during the coming season if the adults are at all numerous when the 
vines “leaf out” in the spring. 
On account of the inability of the nymphs to escape from the under- 
side of the grape leaves and because of the soft and unprotected con- 
dition of their bodies the nymphal period is the most vulnerable stage 
of the insect. Unfortunately this is the stage at which the insects 
are the least conspicuous to the casual observer. For this reason in 
vineyards where the adults are common in early spring an examina- 
tion of the underside of the foliage should be made during the early - 
part of July. If the nymphs are at all numerous a single thorough 
spray application of blackleaf tobacco extract applied to the under- 
side of the leaves before wings are developed will reduce their num- 
bers to such an extent that those remaining will neither seriously cur- 
tail the growth of the vine nor impair the quality of the fruit. 
O 
