292 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 15 



into normal potato leaves. Other leaves were injected likewise with 

 a solution prepared from a leaf showing advanced stages of this dis- 

 ease. Finally, leaves were inoculated with a solution prepared from 

 a leaf that had been killed by hopperburn. By July 25 some of the 

 leaves showed a slight browning at the tip and on July 30 all showed 

 this same type of injury. On August 10 this experiment was closed 

 as the injured area on the inoculated leaves had not increased and they 

 were clearly not affected with hopperburn. The injury in this case 

 was identical with that resulting from multilation and was probably 

 a result of greenhouse conditions. 



Inoculation of Potato Leases with E. malt Extract by Means 

 OF A Hypodermic Needle 



On July 19 approximately 100 Empoasca mali adults of 

 both sexes were collected and m.acerated in 10 cc. of water 

 that had been previously distilled and sterilized. Three potato 

 leaflets wer.e inoculated with the liquid drawn off from this 

 solution and also the petiole of a single leaf was inoculated in the same 

 manner. On July 25 there was a scar or lesion noticed in the mid- 

 vein of each leaf where the needle had been pricked in. At the same 

 time two of the leaves showed decided burning similar in every way 

 to hopperburn, while the third showed the burning less distinctly. 

 The injury increased daily and on July 30 there was no question but 

 that a disease very similar to hopperburn had been produced in every 

 case. On July 29 the above experiment was repeated, using in these 

 inoculations a solution made from 5S adults of both sexes. Part of the 

 leaves in this test were reinoculated 24 hours later by a freshly prepar- 

 ed solution made from .56 adults of both sexes. In this latter test a 

 slip-ht burning was produced but it was in no way com.parable to the 

 injury obtained by the first set of inoculations. Although fewer in- 

 sects were used this was more than compensated for by the additional 

 inoculation the following day. 



On Julv^ 19 approximately 88 nymphs mostly in the fourth and fifth 

 instars were macerated in 10 cc. of water that had been previously 

 distilled and sterilized. Four inoculations were made of which three 

 were in leaf tissue and one in a leaf petiole. Only one of the leaves 

 so treated showed any signs of hopperburn injury, and on this one 

 there was a small brown area at the tip. In all cases, however, there 

 was a marked lesion produced at the point of inoculation. Here the 

 tissue seemed to collapse and the mid-vein became distorted. In 

 dried specimens these lesions are very distinct, showing that the nymphs 



