646 



STATE BOARD OF AGRICULTURE. 



LEAFHOPPER INJURY TO POTATOES 



BY J. E. KOTILA 



Leafliopper injiuy, brought about by the potato leafhopper, has caused 

 losses of thousands of dollars annually to the potato growers of Michi- 

 gan. Investigations at this and other stations show that it is now 

 possible by the use of preventive measures to reduce largely this source 

 of great loss. The importance of the potato crop in Michigan is sucli 

 that an effort should be made to combat this injury. 



The potato ranks third in importance as an agricultural crop, is 

 surpassed only by hay and corn, and is followed by wheat, oats and 

 fruit. Figures obtained from the 14th U. S. Census Bulletin 1920, 

 compiled below, show the position of Michigan as a potato j)roducing 

 state. 



THE POTATO CROP IN VARIOUS STATES 



(*From 14th U. S. Census Bulletin 1920) 



ECONOMIC IMPORTANCE OF SO-CALLED '^''tIFBURN^-' 



Although the total yield of potatoes in Michigan in the 1919 crop was 

 28,929,560 bushels, the average yield per acre was only 85 bushels. This 

 low average yield was caused in large part by a very serious dry 

 weather blighting, the so-called ''tipburn,'' which attacked the tips and 

 margins of the leaves (Fig. 1), giving them a burned appearance and 

 causing a premature death of the vines with consequent reduction in 

 yield. 



Losses from this trouble have no doubt occurred during all seasons 

 of comparative drought, and especially in seasons with temperature de- 

 partures above normal, but attention was first called to it in 1891 by 

 Goff^ While conducting a potato spraying experiment a peculiar 

 "blighting" of the leaves was noted in the check plots which Goff re- 

 ported was not the true potato blight, as there were no indications of 

 the fungus Phytophtliora infestans and no rotting tubers were found 

 when the plots were harvested. Since 1891, however, "tipburn" has 

 been reported as common during hot, dry seasons in all of the more 

 important potato growing states. The trouble was especially severe 

 during the 1919 season and losses up to 25 per cent of the crop were 



