October, ’20] 
DUDLEY: POTATO LEAFHOPPER 
411 
winter in the seed potato, making it easily susceptible to disease when 
planted the following year? 
Control 
All spraying was done with a wheelbarrow sprayer, the spray rod 
fitted with two adjustable arms and two adjustable, angled nozzles. 
All applications were directed upward at an average pressure of 150 
pounds, the material thus being deposited on the under side of the 
leaves as is absolutely necessary. 
Kerosene Emulsion. One plot of Early Ohio and Green Moun¬ 
tain potatoes was sprayed three times with 10 percentage kerosene 
emulsion. 
The infestation of adults was not noticeably reduced. Nymphs , 
present at the time of spraying were readily killed, but great numbers 
continued to hatch and did not appear to be killed by any oil remaining 
on the leaves. There was no repellent effect observed upon adults or 
nymphs. 
The Early Ohios were practically dead from disease by the last 
week in July. The Green Mountains were badly diseased by the 
middle of August. 
The untreated rows of each variety were but little more diseased 
than those treated. 
Nicotine Sulfate. One plot of Early Ohio and Rural New Yorker 
potatoes was sprayed four times with nicotine sulfate 1-1200 and 
fish oil soap 2-50. 
The treatments did not noticeably reduce the infestation of adults; 
eggs continued to be laid and young nymphs appeared without cessa¬ 
tion. Nymphs present when the spray was applied were readily killed 
but no repellent effect was observed later upon either adults or nymphs. 
Disease appeared in this plot a few days after the first spraying. 
On the Early Ohios the disease spread slowly but surely, until the first 
week in August, when all plants were practically dead. One row left 
untreated was at this time diseased to no greater extent than the 
treated rows. 
The Rural New Yorkers, although as heavily infested all summer 
as the other potatoes, remained fairly free of disease. By the middle 
of August, however, the disease began to spread and in a week about 
half of each plant was dead. The untreated row was slightly more 
diseased than the treated one. 
Bordeaux Mixture. One plot of Rural New Yorker and Green 
Mountain potatoes was sprayed four times with Bordeaux mixture 
4-4-50. The infestation of adults and nymphs in this plot was about 
the same as in the previous plots up until the middle of July. From 
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