224 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
THE WORK OF EMPOASCA MALI ON POTATO FOLIAGE 
By P. J. Parrott and R. D. Olmstead 
Summary 
This paper presented details of nine cage experiments and one field 
experiment to determine the effects of attacks of Empoasca mail 
LeBaron on potato foliage. 
In all the experiments, feeding by the insects produced at first small 
brownish areas of one quarter of an inch or more in width at the tips 
and occasionally on the margins of the leaflets. The injury became 
more conspicuous as the season advanced, the brownish or burned areas 
increasing both in extent and numbers. The discoloration progressed 
from the tip towards the base of the leaf, and from the margins towards 
the midrib. As the tissues became desiccated the margins rolled up 
over the upper surface, leaving a small narrow strip of green tissue in 
the central area of the leaflet. In instances where such injuries were 
severe, all the leaflets curled and completely dried up, while the petioles 
often withered and dried so that any slight disturbance produced 
defoliation. 
In the field test the planting comprised forty-two rows that were one 
hundred and eighty feet in length. The variety of potato grown was 
Enormous No. 9. The purpose of this experiment was to determine 
the repellent effects of the usual spraying mixtures upon leafhoppers 
as compared with mixtures of heavier consistency. Applications were 
made of the following preparations: (1), bordeaux mixture (10-10- 
100); (2), bordeaux mixture (10-10-100) with 6 pounds of paste lead 
arsenate; (3), china clay, 60 pounds to 100 gallons of water to which 
were added 10 pounds of soap; and (4), bordeaux mixture (8-8-100) 
with 60 pounds of lump lime. Four rows or more were sprayed with 
each mixture and two rows were reserved as checks. The applications 
were made with a power sprayer at a pressure of 100 to 150 pounds, 
and great care was exercised to cover thoroughly each plant, especially 
the under sides of the leaves. The first treatment was made on July 8. 
As rains had washed to a considerable extent the spraying materials 
from the foliage and the leafhoppers were invading the treated plats, a 
second application was made on July 16. Heavy rains occurred again 
within the next ten days, which necessitated a third treatment on 
July 28. The last application was made on August 25, which later 
developments indicated should have been made earlier and followed 
with another treatment two weeks later. Counts were made of adult 
leafhoppers at more or less regular intervals, which showed plainly 
that all the spraying mixtures had exerted considerable influence as 
repellents. Moreover, at no time during the season were the nymphs 
