President Wilmon Newell: The last paper of this series is by Mr. 

 F. A. Fenton, and is entitled "Further Experiments with Empoasca 

 mali Concerning its Relation to Potato Tipbum." 



PROGRESS REPORT ON THE SEASON'S WORK ON THE 

 PRODUCTION OF POTATO TIPBURN 



By F. A. Fexton, Icnva State College, Ames, Iowa 



During the past season experiments were continued in regard to the 

 production of potato tipbum by the leafliopper, Empoasca mali Le Baron, 

 and ver\' interesting and significant data were obtained. These tests 

 were conducted to determine the effect of artificial mutilation on the 

 potato leaf, the result of colonizing leaflioppers on the plant foliage 

 under different environmental conditions, the comparative effect of 

 different stages of the insect on the leaves, the injury other insects might 

 produce, and the effect of Bordeaux mixture on the leaf-hoppers. 



Effect of Artificial Mutilation on Potato Leaves 



In the first experiment the leaf veins or leaf petioles were mutilated 

 with various instruments. These tests consisted in puncturing the mid- 

 vein with "minnten Nadeln," with finely drawn glass thread, with blood 

 dropper, and with the ovipositor of a hymenopterous insect. The mid- 

 vein was also severed in different places with a scalpel. Individual 

 leaves were mutilated once, twice and three times with the above instru- 

 ments, which were not sterilized. When the leaves were punctured, 

 little or no injury resulted, but when the mid-vein was severed, the leaf 

 showed a distinct type of injury. This was first observed after a period 

 of nineteen days when a triangular area at the tip of the leaf turned 

 yellow and then brown, a condition identical with that of beginning tip- 



