476 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
PART II. PAPERS AND DISCUSSIONS 
Afternoon Session, September iy, 1923 
Following the adjournment of the business session Chairman R. E. 
Campbell opened the regular session and called for the first paper. 
It was presented by Mr. Stahl as follows: 
A DISCUSSION OF EUTETTIX TENELLA BAKER AS A 
CARRIER OF CURLY-TOP OF SUGAR BEETS 
By C. F. Stahl, Assistant Entomologist, Bureau of Entomology, and 
Eubanks Carsner, Pathologist, Bureau of Plant Industry. 
Abstract 
Eutettix tenella when feeding, has the ability under certain conditions to produce 
a systemic disease, known as curly-top in the sugar beet. This ability is acquired 
by the insect after emerging from the egg as a result of feeding for only a short 
period upon a plant already diseased. After this feeding some time must elapse 
before the insect is able to transmit the virus to a healthy plant. This fact indi¬ 
cates that there may be a short incubation period for the virus in the insect. When 
once the ability to produce the disease is acquired there is no evidence to indicate 
that it is ever lost during the life of the insect. Although many insects of species 
other than Eutettix tenella have been experimented with, not one has been found 
that is able to transmit the virus of curly-top. 
Since the announcement by Dr. E. D. Ball in 1906 1 that the beet 
leaf hopper (Eutettix tenella Baker) was responsible for the disease of 
sugar beets known as curly-top, the problem has been the subject of 
practically continuous investigation. As a result of these studies, 
many interesting and important data concerning the relation of the 
insect to the disease have been obtained and reported, but up to the 
present time the nature of the causative agent has not been learned. 
Many of the ascertained points concerning the insect and its function 
in transmitting the disease are suggestive and as they may be of assist¬ 
ance in future work conducted for the purpose of determining the caus¬ 
ative agent for the disease, it is deemed desirable to bring together in a 
brief discussion some of the more important facts relating to this phase 
of the problem. 
This jassid which inhabits the arid and semi-arid regions of the West, 
shows some preference for plants of the family Chenopodiaceae, and 
produces under certain conditions in the sugar beet a systemic disease, 
curly-top. Available evidence indicates that curly-top has been present 
in sugar beet fields in the districts inhabited by this insect from the time 
the beets were first planted there. This crop appears to have been 
selected by the insect because the plants are suitable for oviposition and 
food. 
The ability to transmit curly-top is acquired by the insect after it has 
1 16th Ann. Rept. Agr. Coll. Utah Exp. Sta. for 1905, p. XVI. 
