Washington, D. C. 



UNITED STATES DEPARTMENT OP AGRICULTURE 

 BULLETIN No. 842 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



PROFESSIONAL PAPER 



September 7, 1920 



THE NEMATODE DI 

 CAUSED BY 



EASE OF WHEAT 

 HUS TRITICI 



By 



L. P. BYARS, formerly Pathologist, Office ©f Cotton, Truck, and 



Forage Crop Disease Investigations, in cooperation 



with the Office of Cereal Investigations 



CONTENTS 



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 



