October, ’20] 
DUDLEY: POTATO LEAFHOPPER 
413 
other varieties early in the season, showing principally on the tips of 
scattered leaves. Little more appeared and that present did not 
spread noticeably all summer, even during a period of hot dry weather. 
On Late Puritans and Rurals there was almost no disease; on the rest 
it was very light to light. 
The untreated plot showed signs of disease early but, in contrast to 
the treated plot, the disease spread rapidly until midsummer when 
early varieties were about dead and the late ones were rather badly 
diseased. The Rurals, as in other plots, showed less disease at digging 
time than any other variety. 
Thus the plot given maximum protection, in contrast to the plot 
given no protection, gave abundant evidence throughout the summer 
of the beneficial effect of spraying in relation to leafhopper infestation 
and the resultant disease. 
Yields 
The accompanying table shows the relative yields from each plot. 
No attempt was made to compare the yield from these plots with the 
average yield per acre in the state because the area around Madison 
is not adapted to potato growing and because fertilizers were not used 
on the plots. Yields from untreated plots were arbitrarily called 
100 bushels. 
Table Showing Yields 
Untreated rows 
Treated rows 
Bu. per acre 
Bu. per acre 
Kerosene Emulsion Plot: 
Early Ohio. 
100 
166 
Green Mountain. 
100 
125 
Average. 
100 
146.5 
Nicotine Sulfate Plot: 
Early Ohio. 
100 
150 
Rural New Yorker. 
100 
200 
Average. 
100 
175 
Bordeaux Mixture Plot: 
Rural New Yorker. 
100 
200 
Green Mountain. 
100 
196 
Average. 
100 
198 
Bordeaux-Nicotine Plot: 
Early Triumph. 
100i 
100 1 
Early Ohio. 
100 
196 
Irish Cobbler. 
100 
277 
Green Mountain. 
100 
233 
Late Puritan. 
100 
217 
Rural New Yorker. 
100 
185 
Average. 
100 
221.6 
1 Practically no marketable potatoes. Not included in average. 
