408 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
four. A minimum length of time between molts was one day, as 
noted for the second, third, or fourth instars, during July, while a 
maximum of eight days’ duration for the fifth was observed during 
October. 
The duration of the nymphal or larval period varied greatly during 
the different months. In July the insect spent only a week maturing 
while in September and October, due to cool weather, the nymphal 
stage was prolonged to twenty-six days. This gave a minimum of 
fourteen days during July as the cycle from egg deposition to adult 
and a maximum in September and October of forty days. Thus the 
total life cycle was ten weeks for the first and over a year for the second 
generation. 
CONTROL OF THE POTATO LEAFHOPPER (EMPOASCA MALI 
LE B.) AND PREVENTION OF “ HOPPERBURN ” 1 
By John E. Dudley, Jr., Scientific Assistant, Bureau of Entomology, U. S. Depart¬ 
ment of Agriculture 
Introduction 
Although periodic outbreaks of a leafhopper, probably the potato 
leaf hopper (Empoasca malt), have occurred in this country since the 
early eighties, the insect’s association with a disease of potato has just 
been established by Ball. 2 
As with most insect borne diseases it is the disease which we dread 
far more than the primary feeding injury of the insect involved. 
The summer of 1919 was a most opportune time to undertake studies 
of disease transmission and control of the potato leafhopper. The 
infestation and accompanying disease had been severe in 1918, promis¬ 
ing to be equally as bad the next year. Evidence that a disease 
formerly included in the term “tip burn” was transmitted by the 
insect had just appeared. Therefore, the problem was attacked in 
earnest and all possible data secured on the study of the insect itself, 
its relation to various hosts, and the effect of treatments used against 
it. Special emphasis was placed on the phase of most economic im¬ 
portance—transmission of disease and control. 
Disease Transmission 
The first outward indication, of the disease, “hopperburn” (Plate 9), 
is a slight yellowing, usually at the tip of a leaf, followed by curling 
1 Published by permission of the Secretary of Agriculture. 
2 Ball, E. D., “The Potato Leafhopper and the Hopperburn That It Causes,” in 
Wise. State Dept, of Agric. Bui. No. 20, 1918. 
