Experiment station reports. 30? 



and Streak diseases of the potato. Experiments were also conducted to 

 determine whether the Leaf Hopper, Empoasca mali, was responsible 

 for the burning of the tips and margins of the leaves commonly known 

 as "tipburn." As Blackleg during seasons favorable to the disease 

 results in losses of from 10 to 75%, the major part of the time was spent 

 investigating this disease. Hill selections were also made during the 

 growing season to determine whether Mosaic, Leaf Koll and Streak 

 diseases are disseminated from diseased to neighboring hills, the tubers 

 from these selections being saved for 1920 planting. 



The work during the 1920 season has been a continuation of the work 

 started in 1919 and in addition has been supplemented by life history 

 studies of the Potato Leaf Hopper, Empoasca mali, and spraying experi- 

 ments with Bordeaux mixture for its prevention. Experiments were also 

 conducted to determine whether potato diseases are disseminated by 

 potato plant lice and leaf hoppers. 



The field Avork has been supplemented by work in the laboratory on 

 isolation and study of the causal organisms of the various potato dis- 

 eases, approximately one-half of the investigator's time being devoted 

 to field work and one-half to laboratory researches. 



J. E. KOTILA, 



Eesearcli Assistant in Plant Pathology. 



