82 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 14 



Here we have the same insect, as far as anybody knows, producing an 

 entirely different effect on another plant. And in this connection I want 

 to say that we are studying the physiology of leaf spots on various plants 

 caused by leaf-hoppers and plant-hoppers, and we find a great many 

 of the spots that have been described in pathological literature are 

 intimately bound up with these peculiar kinds of insects, but we know 

 very little about the real physiology behind these things as yet. 



Mr. T. J. Headlee; One year ago this summer I asked Professor 

 Ball about the diagnostic characters of this kind of injury. He gave 

 them to me very much as they were stated to-day. I used the informa- 

 tion to examine the conditions in our state. We raise about 15,000,000 

 bushels of potatoes, and I found some leaf-hopper injury, but I did not 

 fine leaf-hopper injury or leaf-hopper bum as the principal source of 

 what the plant pathologists usually call tip-burn. 



Mr. J. G. Sanders : I had the privilege, last simimer, of observing in 

 Holland some very extensive experiments along this very line. Potatoes 

 of similar varieties were similarly caged in cages of similar sizes made up 

 of glass, wire and cloth. Invariably those potatoes with hoppers had 

 tip-burn. 



Mr. p. J. Parrott: It may be of interest to Dr. Headlee to hear of 

 an experience with tip-bum in New York. In 1908 the leaf hopper was 

 very abundant on potatoes, and much browning of the foliage was noted 

 in plantings where the insects were numerous. Injuries to the foliage 

 were diagnosed by a phytopathologist as typical tip-bum, which identi- 

 fication by the way, mislead us as to the destructive capacities of the 

 insects. In planning for field experiments with the leafliopper in 1919 

 we secured the assistance of a phytopathologist, who noted the occur- 

 rence of various diseases in the different plats. As some of you know, 

 the unsprayed rows or checks were practically destroyed. The brown- 

 ing of the foliage was almost entirely due to the work of the leafhopper 

 and Mr. Stewart, our phytopathologist, has gone on record as saying 

 that the diseased condition of the check plants was not distinguishable 

 from what he has heretofore designated as tip-burn. 



Mr. H. a. Gossard: I want to make one or two observations as to 

 the cost of preventing tip-burn. It wotild appear to me that the cost 

 of preventing tip-burn might exceed the value that you get in increased 

 yield, yet because of the fact that leafhopi3ers are also concerned in 

 transmitting fungus and bacterial disease, I would regard the appear- 

 ance of tip-burn in a potato-patch as a good hint to get busy, regardless 

 of the fact that it might cost more to prevent tip-burn than to suffer 

 from it, because I might be preventing something much more costly 

 than tip-bum. 



