LAWSON : KANSAS CICADELLID.^. 19 



Not very much has been done on the relation of insects to 

 the transmission of Bacillus amijlovorous which causes "fire 

 blight." Doctor Merrill has worked on the relation of aphids 

 to the spread of this disease, and Mr. F. H. Lathrop has done 

 some work on the relation of Empoasca mali to the same dis- 

 ease. The latter reports that while in the tests Empoasca uni- 

 color and Typhlocyba rosas showed negative or doubtful results, 

 Empoasca mali seemed to be a positive agent in the spread of 

 the bacteria and in the infecting of new shoots. Should this 

 work be confirmed we would have a practically untouched field 

 opened to us, which, with careful work, might better enable 

 us to be victors in the fight against this serious disease. 



But we are not yet through with Empoasca ynali. Again it 

 is under indictment, this time for producing what should be 

 called "hopperburn," especially on potatoes. Here again we 

 are indebted to Doctor Ball, who seems to have shown that 

 this insect produces much of what in the past has gone 

 under the name of "tipburn." Furthermore, that hopperbura 

 is perhaps a disease similar to curly-leaf, and that it differs 

 from tipburn by readily-told characteristics, the latter being 

 the result of purely physiological conditions. In the past two 

 summers great damage has been done by this disease, if such 

 it shall prove to be, but for which this leaf hopper alone seems 

 responsible. 



Again, leaf hoppers may piove to be disseminators of fungous 

 diseases. Any insect of course may play this role, but because 

 of their feeding and egg-laying habits, combined with their 

 jumping disposition, they seem to be especially suited to trans- 

 mit such fungi from plant to plant and thus spread the dis- 

 ease. This is a field as yet untouched that might yield dis- 

 coveries of importance to the agriculturist and horticulturist. 



Perhaps this discussion of the economic importance of the 

 group would not be complete without a brief resume of the 

 methods of control. This consists in using natural farming 

 methods and spraying. The chief ways to control the species 

 damaging forage and grain crops would be those of rotation 

 and clean farming. These of course are the best for the soil 

 and are also the way to check insects. ]\Iost of such forms 

 hibernate in the e^g stage under the sheath of the grass blades. 

 If therefore the places where such grasses occur, such as the 

 fence and hedge rows, the corners, and land adjoining fields, 



