392 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



fruits for the control of canker worms provided the weather conditions 

 are favorable. It is not recommended, however, for general practice as 

 there can be no guarantee of what the weather may be after the 

 application of the arsenical. 



3. It is very strongly recommended, when necessary to use an arsenical 

 upon stone fruits, that the basic type of lead arsenate be used exclusively. 

 In order that this slower acting poison may be effective, it will be 

 necessary to keep a close watch of the orchards and make the applica- 

 tion while the worms are very young. 



WILD VEGETATION AS A SOURCE OF CURLY-TOP INFEC- 

 TION OF SUGAR BEETS 1 



By P. A. BoNCQUET, Bacteriologist, Collaborator,^ and C. F. Stahl, Scientific Assistant, 

 Truck Crop and Stored Product Insect Investigations, Bureau of Entomology 



The curly-top condition of sugar beets has for some time been a 

 subject of investigation by phytopathologists, but on account of 

 the failure to discover a specific organism responsible for the physio- 

 logical injury to the plant, the problem has been peculiarly baffling. 

 Although the connection of the jassid leaf hopper, Eutettix tenella 

 Baker, with the disturbance has been definitely established, conclusive 

 evidence has not previously been available as to the exact nature of 

 the trouble, or as to the part played by the leafhopper in the dis- 

 semination of the virus. It is believed that the results secured as 

 herein related may be of assistance in establishing in part the nature 

 of the disorder, the identity of its probable alternate hosts and the 

 conditions governing its somewhat periodical or sporadic appearance 

 in beet fields. 



A brief review of the investigations leading to the experiments 

 which will be mentioned may serve to emphasize the significance of 

 the results obtained. 



The connection of Eutettix tenella, known both as the sugar-beet 

 leafhopper and the curly-top leafhopper, with the condition was first 

 definitely established in 1909.^ Soon afterwards it was found that a 

 single leafhopper in any stage was capable of producing the condition 



^ Published by permission of the Honorable Secretary of Agriculture. 



2 Since this article was first presented for pubhcation, Doctor Boncquet has been 

 absent in Argentina. He has not, therefore, had the opportunity of approving 

 some of the corrections in the manuscript. 



3 Ball, E. D. The Leafhoppers of the Sugar Beet and Their Relation to the 

 "Curly-leaf" Condition. U. S. Dept. Agr. Bur. Ent. Bui. 66, pt. 4, p. 33-52, pi. 1-4, 

 1909. 



