80 JOURNAL OF ECONOMIC ENTOMOLOGY Vol 14 



Mr. R. L. Webster: I made some chemical tests recently on the 

 effect of red spiders on the foliage of roses. There seems to be an 

 accumulation of mucilages and pentosans; substances that take up 

 water. That may be a factor in this situation. 



Mr. J. E. Dudley, Jr.: An experiment at Madison, Wisconsin, this 

 year might be of interest in connection with the previous papers. Indi- 

 vidual plants of five varieties of potatoes were caged, two cages to each 

 \'ariety. In one cage over each variety there were about twenty adult 

 leafhoppers placed the 12th of July. The other cages remained free of 

 leaf hoppers the whole season. In every case hopper-bum occurred in 

 the cages in which leafhoppers were placed and in no case did it occur 

 in cages which were kept free from them. In the cages in which it 

 occurred it was not nearly as serious per variety as in the rest of the field, 

 which would look as though the partially decreased transpiration in the 

 cages retarded the spread of hopper-bum. 



Potato flea beetles and potato aphids were found in all the cages. 

 It was impossible to keep them out. As no hopper-bum occurred in the 

 check cages, it would look as though we could eliminate these two insects 

 as causal agents. 



My experiments differ slightly in one respect from Mr, Fenton's; 

 that is the rate of spread of hopper-bum. Observations would appear 

 to indicate that hopper -burn will spread over a whole plant once the 

 plant has been affected. I have seen that in several cases where one 

 or two hoppers were placed on a plant for a week, sav, and then taken 

 off and the plant continued to droop until it was entirely dead. 



Mr. F. a. Fenton: We tried that experiment time and time again 

 and we absolutely did not get any tip-burn. We caged a plant with 

 adult leafhoppers and we knew that this plant was loaded with eggs. 

 The hatching young were transferred from the leaves every twenty-four 

 hours and no tip-burn was noticed. We had counts as high as several 

 hundred young from one plant and A-et when we removed these ever}' da 3^ 

 we did not get any tipburn. 



Mr. T. J. Headlee : I would hke to know from Mr. Eyer whether 

 there was any late blight connected with the experiments that would in 

 any way influence the yield. 



I would like to know from the last speaker whether tip-bum in his 

 opinion is ever caused by any other agency than the hopper. I would 

 like to know from Mr. Fenton what he considers the diagnostic charac- 

 ters of hopper-burn. 



Mr. J. R. Ever: In answer to Dr. Headlee's question regarding the 

 matter of late blight, according to our plant pathologist who is located 



