B. r. I.— 261. 



THE CONTROL OF TEXAS ROOT-ROT OF COTTOX." 



Bv C. L. Shear, Pttlholot/ist, ami CiEORciK F. Mii.ks, Srimtijir Assistant In I'lilhologi/. 



INTRODUCTION. 



Root-rot, or the so-callod 'clyin^^" of cotton, is each year becommg 

 a more and more serious enemy of the cotton grower in Texas and 

 other parts of the Southwest. It has not yet been found east of Texas, 

 but it is likely to spread gradually eastward. The extent of its dam- 

 age to the cotton crop during the past season (1906) was apparently 

 o-reater than ever before. It has been estimated that the total loss 

 caused by this disease in Texas last year was about S3,000,000. Dur- 

 ing seasons favorable to the development of the parasite it increases 

 its area of destruction quite rapidly. Some cotton planters have 

 expressed the opinion that this disease is at present a more serious 

 menace to the cotton crop of Texas than the l)oll weevil. 



Root-rot is not restricted to cotton, but attacks a large number of 

 other cultivated and wild plants. 



CAUSE OF ROOT-ROT. 



The disease has been attributed by j^lanters to a variet}^ of causes. 

 Our investigations have shown, however, that it is primarily due to a 

 fungous parasite which lives and spreads in the soil. This fimgus is 

 known as a species of Ozonium and is most prevalent and mjurious in 

 the Houston clay or black waxy soils of the Southwest. Under favor- 

 able conditions of temperature and moisture, the fungus attacks the 

 roots of the cotton plants, destroying the rootlets and external surface 

 of the roots and also invading the fibro-vascular system, thus causing 

 the plants to suddenly wilt and die. This organism grows best where 

 the aeration of the soil is poorest. The disease may be easily recog- 

 nized by the sudden wilting and dying of the plants and the presence 

 on the loots of dirty yellowish strands or a thm weft of the fungous 

 filaments. 



oThe results of the field experiments conducted by Doctor Shear and Mr. Miles 

 last season (1906) were so promising that it is deemed desirable to present them to 

 cotton growers at once. Further time will be required to complete the investigations 

 and demonstrate more exactly the value of the method recommended. — B. T. Gallo- 

 way, Pathologist and Physiologist, and Chief of Bureau. 



102— V 



89 



