Februar}-, '21] marcovitch: potato leaf hopper 61 



THE POTATO LEAF-HOPPER AND TARNISHED PLANT 

 BUG IN 1916 



By S. ^iARCOVITCH, Knoxville, Tenn. 



Ball records in this Journal a severe epidemic of the potato leaf- 

 hopper on potatoes in Wisconsin for the summer of 1918. In a series 

 of splendid experiments he also proves that the causative agent is the 

 potato leaf-hopper, Empoasca mali Le B., and not the so called tipbum. 



The writer had reached the same conclusion during the simimer of 

 1916 when connected with the Minnesota Experiment vStation. The 

 results were published in the Princeton Union August 24, 1916, describ- 

 ing "havoc in the potato fields," in the vicinity of Princeton. Minnesota. 

 Mr. Saxon a potato farmer in Princeton, called our attention to the 

 hoppers. It was only his insistence that the bugs were the cause of the 

 damage, that caused more accurate observations to be made. As far 

 back as 1911, Mr. Saxon reports that he noticed the leaf -hoppers injuring 

 his potatoes, causing as much as 35 per cent, damage. Several weeks 

 in the field were devoted to studying and experimenting with hopper- 

 dozers and spraying. 



In Minnesota, the Triumph ^'ariet^- suffered most severely. The 

 leaves were dying so rapidly that a perceptible decaying odor could be 

 smelled. From 350 to 500 leaf-hoppers and about 50 tarnished plant 

 bugs were coimted on a single vine. In addition to the regular potato 

 leaf-hopper, Empoasca malt, there were also present in some numbers 

 two other leaf-hoppers, DeHocepha'us ininiicus and Cicadula 6-notata 

 as well as a large brown DrosophiJa, probably attracted by the decaying 

 odor. It was noted that the leaf -hoppers suck on the small veins causing 

 the leaf to curl along the margin while the tarnished plant bugs suck on 

 the midrib or the tip of the growing shoot causing the leaf to curl up- 

 wards or the shoot to wilt entirely. If the stem of a shoot that has been 

 stung by the tarnished plant bug is cut open, it will be found to be 

 rotten. \^er}- often a distinct swelling can be noted on the stems. 

 Later varieties, such as the Burbank, did not suffer badly probably be- 

 cause they are not so tender as the Triumph, or as Ball observed that 

 not enough foliage is present for egg deposition of the spring brood. 

 During the early part of September wet rainy weather set in. The 

 leaf-hoppers promptly disapppeared and many were noticed clinging to 

 leaves, having been attacked by a fungus. Observations were made on 

 early Ohios in the western part of the state in the vicinity of Moorhead. 

 No burning was found and but \^ery few leaf -hoppers 'were noticed. 

 The season was wet there and this probably accounts for their 

 absence. 



The work in regard to the control consisted in running a hopper- 

 dozer over 20 acres of potatoes. Both kerosene and tanglefoot were 



