August, ’23] 
VAN dine: effects of leafhopper on grapes 
355 
applied to the under sides of the leaves under strong pressure. The 
plots were sprayed July 17th to 19th, inclusive. 
In the grape section under consideration, there was an average in¬ 
festation of 64.25 leaf-hopper nymphs per leaf on the maximum in¬ 
fested vines, including both upper and lower leaves, at the time the 
nicotine spray was applied. Twenty-four hours after the nicotine spray 
was applied, a count of tagged companion leaves on all the plots gave an 
average of 18.37 nymphs per leaf, a reduction of 71.40% in the numbers 
due to the nicotine spray. 
The analyses of grapes made by Hartzell in 1913 suggested to the 
writer that the sugar content of the grapes in the demonstration plots 
receiving the nicotine spray, would be an index to the efficiency of this 
control measure. Readings by the Brix spindle were taken of the 
juice from composite samples of grapes from all the plots. The amount 
of nicotine and the time of application were the same for all the plots. 
There was a variation in the method of application, in the amount of 
leaf-hopper infestation, in the pressure maintained, in the extent of 
vine growth, and in the height of the foliage on the wires above the 
ground. The composite samples were taken (1) from the portions of the 
plots indicating maximum leaf-hopper infestation, and (2) from portions 
a reasonable distance from such locations. In addition to the com¬ 
posite samples from each of the plots, selected samples were taken from 
vines showing the best production and condition of the fruit. The 
following table gives the results of the Brix readings of the juice from 
the grape samples taken from the six plots. 
Table I. Brix Readings, Nicotine Sprayed Grapes, Concord Variety 
Brix Reading. 
Vineyard 
Composite samples. 
Selected 
1st. 
2nd. 
Average. 
samples. 
Luce. 
17.89 
15.77 
16.-83 
17.94 
McCord. 
16.19 
17.29 
16.99 
17.39 
South wick. 
17.99 
17.67 
17.83 
19.07 
Bostwick. 
16.87 
19.07 
17.97 
17.97 
Pierce. 
19.07 
19.27 
19.17 
20.17 
Bernet. 
19.87 
20.27 
20.08 
19.57 
Average of totals. 
18.06 
18.22 
18.14 
18.68 
