62 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



used for the catching mediums. A great many leaf -hoppers were caught 

 but figuring 400 to a plant we caught probably one percent. The hop- 

 pers would fly over the machine and under and at times the driver could 

 hardly see his way thru the cloud of insects dancing over the machine. 

 Our work, at best, demonstrated the utter uselessness of the hopper- 

 dozer for the control of the potato leaf -hopper. 



Spraying experiments were also carried out using kerosene emulsion. 

 A 15 to 1 emulsion gave no results, neither did a 10 to 1. The only 

 thing we could get to kill them was a 2-to-l or pure, kerosene. The latter 

 two did not injure the vines. When Professor Moore learned that we 

 had used pure kerosene without injury to the plants, he set out to 

 determine the cause and gave us his results (Jour. Econ. Ent. 11:70) 

 showing that kerosene is a ver\' variable product in regard to boiling 

 points and toxicity. 



It was planned to make further cage experiments such as Ball did to 

 prove absolutel_v and beyond doubt that the leaf-hopper is the cause of 

 the burning of the potato leaves, but the writer left Minnesota to enter 

 another field shortlv afterwards. 



President Wilmon Newell: The next three papers bear on the 

 same subject. If there is no objection, discussion will be deferred until 

 their reading has been completed. 



The first is by Mr. Albert Hartzell on "Further Notes on the Life 

 History of the Potato Leafhopper." 



FURTHER NOTES ON THE LIFE HISTORY OF THE POTATO 



LEAFHOPPER 



(Empoasca rnal: Le Baron) 



B}- Albert Hartzell, Iowa State College, Ames, Iowa 



Dr. Ball's^ discovery that the potato leafhopper is responsible for the 

 disease called tipburn was the first step in removing the subject from 

 conjecture and directed serious attention to the study of the insect as 

 the key to the solution of the problem. Little was known regarding the 

 life history of this species because of the difficulty experienced in keeping 

 the adults and n\TTiphs in captivity a sufficient length of time to rear a 

 complete generation. For the last two years the Iowa Experiment 

 Station has been conducting a study of this insect and as some of the 

 first year's work has been published- it is the purpose of this discussion 

 to give only a brief summary of additional information obtained during 

 the growing season of 1920. The work was done under the direction of 



'Ball, E. D., Wis. Dept. Agr., Bull. 2:i, pp. 76-102, 1919. 



^Fenton, F. A., and Hartzell, A., Jour. Ec. Ext., Vol. 13, No. 4, pp. 400-40S, 1920. 



