6 BULLETIN 618, U. S. DEPARTMENT OE AGRICULTURE. 



Plains. Aii apparent exception to this high-yielding power under 

 drought conditions was noted at several stations in the two very dry 

 years, 1910 and 1911. In these years the durum wheats produced 

 relatively low yields. This was found to be due, however, not to 

 lack of drought resistance, but to sterility caused by a combination 

 of climatic conditions, including drought and hot winds coincident 

 with the flowering period of durum wheat. The floral organs were 

 injured, and the kernels did not develop, much reducing the yields. 

 On some of the same stations durum- wheat which was sown later in 

 the spring and had not reached the flowering stage at the time hot 

 winds occurred was not injured, although exposed to all the other 

 drought conditions. 



Many varieties of durum wheat are somewhat resistant, and cer- 

 tain varieties very resistant, to attacks of stem rust (Puccinia gram- 

 inis Pers.). The varieties now grown commercially are subject to 

 more or less infection on the sheaths and leaves, while the peduncle, 

 or neck, often remains fairly free from such infection. This allows 

 the development of a fairly plump kernel under rust conditions which 

 cause serious injury to the common wheats. 



The durum wheats also are less subject to smut than the spring 

 common wheats. Bunt, or stinking smut ( TiUetia foetens (B. and C.) 

 Trel. and T. tritici (Beij.) Wint.), rarely affects durum wheat, al- 

 though the loose smut ( Ustilago tritici (Pers.) Rost.) occurs about as 

 frequently on durum as on common wheats. 



There are some objections to the growing of durum wheat, wholly 

 apart from market considerations. The long stiff beards are such a 

 source of discomfort in handling the crop that many farmers object 

 to growing it on that account. However, the increasing use of ma- 

 chinery in harvesting and thrashing is gradually removing this objec- 

 tion. The spike or head in the durum wheats is so compact that it 

 dries very slowly after rains or heavy dews. This makes the durum 

 varieties susceptible to the attacks of scab (Fusarium culmorum 

 (W. Sm.) Sacc.) and other imperfect fungi. These fungi sometimes 

 affect durum wheat rather seriously. 



The durum wheats have come from countries of low rainfall and 

 fairly high summer temperatures, where loss of moisture by evapo- 

 ration is rapid. The results of many experiments show them to be 

 valuable under similar conditions in the northern Great Plains in 

 this country. On account of their ability to produce well in the 

 presence of rust infection, they also are valuable and widely grown 

 in the subhumid portions of the Dakotas and western Minnesota. 



PRODUCTION. 



The varieties of durum wheat introduced by the United States 

 Department of Agriculture in the years 1898 to 1900 were distributed 

 to farmers as well as to experiment stations. The new introductions 

 soon became popular among farmers of the northern Great Plains. 



