UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 842 
Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 
Washington, D. C. 
PROFESSIONAL PAPER 
September 7, 1920 
THE NEMATODE DISEASE OF WHEAT 
CAUSED BY TYLENCHUS TRITICI 
By 
L. P. BYARS, formerly Pathologist, Office of Cotton, Track, and 
Forage Crop Disease Investigations, in cooperation 
with the Office of Cereal Investigations 
CONTENTS 
Page 
Occurrence of the Disease ..... 1 
History 2 
Distribution 4 
Economic Importance 6 
Description of the Disease 6 
Differences between This Disease and 
Tulip-Root 8 
Origin and Description of the Galls . 9 
Cause of the Disease 10 
Page 
Effect of High Temperatures on the 
Larva; 19 
Effect of Chemicals on the Larvae. . . 24 
Overwintering of the Parasites ... 27 
Host Plants 28 
Methods of Spreading the Parasites . 30 
Methods of Control 32 
Summary 35 
Literature Cited 37 
WASHINGTON 
GOVERNMENT PRINTING OFFICE 
1920 
