4 THE CONTROL OF COTTON WILT AND EOOT-KNOT. 



are affected. Beyond the places where the cotton is killed, dwarfed 

 or stunted plants occur. Some plants remam alive in the worst 

 areas, and by selection from such individuals resistant varieties 

 have been developed. 



Cotton wilt is more full}^ described in Farmers' Bulletin 333, 

 entitled "Cotton Wilt," which will be sent free upon application to a 



Fig. 2-— Cross sec- 

 tions of cotton 

 stem. showing 

 browning of 

 wood caused hy 

 the wilt fungus. 

 (Natural size.) 



Fig. 3.— Roots of cotton, showing en- 

 largements caused liy the galhvorm. 

 Owing to the wide prevalence of this 

 worm in the southeastern I'nited 

 States, the aggregate annual damage 

 which it causes on cotton is very large, 

 though not generally appreciated. 

 (After George F. Atkinson.) 



Fig. 4.— Roots of okra, show- 

 ing the enlargements caused 

 by the galhvorm. The nem- 

 atodes producing tliis dis- 

 ease are to be found in the 

 root enlargements. (After 

 J. C. Neal.) 



Senator, Representative, or Delegate in Congress, or to the Secretary 



of Agriculture. 



HOW TO RECOGNIZE ROOT-KNOT. 



Wliere root-knot occurs* with wilt the injury from the latter is 

 (Teatly increased. Root-knot itself does not show on the above- 

 ground parts of the plant except through its mdu'ect injury, and hence 

 is frequently overlooked. 



It is desirable that the farmer know with certainty whether there 

 is root-knot in his land. As a test, okra, tomatoes, or cantaloupes 

 may be planted and the roots dug up after midsummer and examined 

 for swellings or galls. If these are found, a rotation of plants immune 

 to root-knot should be started to get rid of the pest. (See p. 7.) 



[Cir. ftU] 



