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JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
It is seen from the table that the treated rows gave much higher 
yields, ranging from one-fourth higher with Green Mountains, sprayed 
with kerosene emulsion, to two and three-fourths times as high with 
Irish Cobblers, sprayed with Bordeaux-nicotine. 
However, as the four plots were widely separated and varied as to 
soil and previous manuring, the relative yields are not as indicative of 
the best spray as was the amount of disease which existed on the foliage. 
Rural New Yorkers showed less difference in yield from three kinds 
of treatment than any other variety. They were also diseased less 
than any other kind. That it payed to spray them, however, is clear. 
Number of Applications Necessary 
It is believed that at least three applications, and preferably four, 
should be made. The first should be applied when leafhoppers have 
come in numbers. 
The second spray should be applied in from ten days to two weeks 
from the first. Potato plants are growing rapidly at this time, offer¬ 
ing new foliage to leafhopper attack. Frequent rains may be expected 
in some sections of the country, and will wash off much of the material. 
The third spray should usually be applied about two weeks after 
the second, the exact time depending upon the amount of new growth 
infested, abundance of leafhoppers, weather conditions. (Hot dry 
weather is very favorable to rapid spread of the disease.) 
A fourth spray might well be given to advantage when some of the 
following conditions exist: a hot dry summer, heavy new growth in 
late summer, great abundance of leafhoppers, desire to control certain 
other potato diseases. 
When leaf-eating insects occur with the potato leafhopper, an 
arsenical can usually be combined with one or more of the Bordeaux 
sprays. 
Enemies 
Two enemies of the potato leafhopper were in evidence during the 
past season. One, a hymenopterous parasite, probably a Dryinid, 
attacked leafhopper eggs. It occurred in too small numbers to be of 
practical benefit. 
The other enemy, a fungus (Entomophthora sphaerosperma ), attacked 
both adults and nymphs. It was common all over the state and in 
northern sections greatly reduced the infestation. 
Conclusions 
Of three materials tested by themselves, Bordeaux gave by far the 
best results in leafhopper control and disease prevention. The yield 
