6 BULLETIN 842, U. S. DEPARTMENT OF AGRICULTURE. 



ECONOMIC IMPORTANCE. 



Economically this wheat disease is of considerable importance in 

 certain countries and of very minor significance in others. In cen- 

 tral Europe, especially in Germany, where the trouble was found soon 

 after its discovery in England, reports during the last decade indi- 

 cate that the disease caused little damage. Earlier writings, how- 

 ever, show that it was responsible for severe losses. Haberlandt 

 (15) in 1887, for example, reported that of 3 samples of wheat 

 collected from as many Provinces in eastern Germany, 20 contained 

 considerable quantities of the diseased kernels. 



Doubtless improved methods of cultivation and sanitation and 

 the general agricultural practices in combination with a knowledge 

 of means of controlling the disease are responsible for its apparently 

 minor economic status in central Europe in recent years. In Eng- 

 land, where conditions seem to have been rather favorable for its 

 development, the malady now appears to be well controlled, al- 

 though, as in Continental Europe, writers during the eighteenth 

 century report its serious prevalence at times. Judging from the 

 examination of small lots of wheat shipped from Russia, Turke- 

 stan, and India, it occurs in these countries to a considerable ex- 

 tent. Reisner 1 in 1915, without knowing its cause, reported that 

 the malady at that time was the cause of severe losses in certain parts 

 of China. 



During the past year the disease has been found to be the cause of 

 heavy losses at certain places in the United States. Lots of wheat 

 sent in from or collected by the United States Department of Ag- 

 riculture in Virginia contained, according to count, from a fraction 

 of 1 per cent to more than 50 per cent of the nematode galls. These 

 findings, together with the fact that many of the galls are lost be- 

 fore and during thrashing and that there are many direct losses 

 caused to the crop in the field by the disease not shown by the 

 thrashed grain, suggest much more severe damage than that indi- 

 cated by the percentage counts referred to above. During the sum- 

 mer of 1918 the writer found several fields in one locality in Vir- 

 ginia in which about half of the wheat heads were severely infected, 

 and, in addition, many of the plants were killed. 



DESCRIPTION OF THE DISEASE. 



The nematode disease of wheat manifests itself only on the aerial 

 parts of the host. It affects directly both the young and old leaves 

 as well as the embryonic fruit, and may indirectly cause a bending 

 or crooking of the stem. On seedlings mildly infected it usually 



1 Dr. II. .T. Reisner, of the University of Nanking, Nanking, China, in a letter trans- 

 mitting specimens to the Office of Cereal Investigations, states that the disease causes 

 great damage in some Chinese Provinces. 



