A NEW DISEASE OF WHEAT 



By Erwin F. Smith, 



Pathologist in Charge, Laboratory of Plant Pathology, Bureau of Plant Industry, United 



States Department of Agriculture 



The appearance in our Middle West of a new disease of wheat (Triti- 

 cum spp.) is a matter of much concern. It is yet too early to map its 

 distribution, but it has appeared in parts of Indiana, Arkansas, Kansas, 

 Oklahoma, and Texas, and is believed to be present in other States. 



I have been aware of the existence of this disease since 1902, hav- 

 ing that year received a few diseased wheat spikelets from Indiana 

 (courtesy of Dr. J. C. Arthur) with the statement that the inclosed might 

 be of interest to me. It was then identified as probably a bacterial dis- 

 ease, but was not supposed to be one of any great importance. Since 

 that year I heard nothing more concerning it until 191 5, when abundant 

 material was received in June from Kansas (courtesy of Mr. I,eo E. Mel- 

 chers), and again from Indiana (courtesy of Dr. H. B. Humphrey, of 

 Cereal Investigations, Bureau of Plant Industry). 



This year (1917), owing to the great slump in the 5deld of winter wheats 

 in our Middle West (estimated at 150,000,000 bushels, and generally 

 ascribed to winter-killing), I suspected that a part of the loss might be 

 due to this new disease, and have sent three men into Texas, Oklahoma, 

 Kansas, Arkansas, Missouri, and neighboring States to make an ex- 

 ploration. From each of these men I have received hard wheats showing 

 the disease. 



From the fact that it occurred in Indiana 15 years ago, it seems 

 probable that this disease has existed in our wheat fields for many years 

 unrecognized, either altogether overlooked or, what is more likely, con- 

 fused with other wheat diseases. First, in 191 5, probably under specially 

 favorable weather conditions, it developed to such an extent as to 

 attract general attention and frighten many farmers, especially in 

 Kansas. 



From the little we yet know it is not possible to predict its future 

 course nor to pronounce positively as to its cause, although from the num- 

 ber of bacteria present in the spots, bacteria which are sometimes so 

 abundant as to ooze to the surface in honey-like small drops, drying as 

 crusts, and from the fact that the poured plates this year have yielded the 

 same organism as in 191 5, I believe it to be of bacterial origin. Should 

 it increase, or even continue to prevail as extensively as in 191 5 and 

 this year, it will have to be reckoned with as a very serious disease of 

 wheat, not as destructive as the rusts but more destructive than the 



Journal of Agricultural Reasearch, Vol. X, No. i 



Washington, D. C. July 2, 191 7 



ii Key No. G — 115 



(51) 



