COTTON 109 



reported from the East Indies, but Butler, who has made 

 the most recent investigations on this subject, is of 

 the opinion that N. vasinfecta is not the cause of the 

 wilt disease upon any of these plants or upon the 

 cotton. He believes N. vasinfecta to be a soil sapro- 

 phite, and that these diseases are due to Fusaria 

 whose perfect stages are as yet undetermined. 



The nature of this organism is such that no direct 

 treatment can be given. The diseased plants should be 

 destroyed as soon as they begin to wilt if possible. If 

 not possible to do this the old and dead plants should 

 be burned at the close of the season. When the disease 

 is very severe the crops should be rotated, and the fields 

 kept in some other crop for as long a period as practical. 

 Fertilizers suitable to the development of strong healthy 

 plants should be used. However, the most satisfactory 

 remedy up to the present time has been the develop- 

 ment of resistant varieties. These have proved especially 

 successful in the United States. 



Black Rust ; Yellow Leaf Blight ; Mosaic Disease. 

 This is one of the most interesting and most complex 

 diseases of the cotton, and in the United States it is by 

 far the most important. It is the result of a number of 

 factors, primarily the soil and the climate, which, if 

 unfavourable, so weaken the plants as to make them 

 easy victims of any one or more of the following fungi : 

 Macrosporium nigricaulitum, Atk., Alternaria sp., 

 Mycosphaerella gossypina, Atk., and Glomerella 

 gossypii, (Southworth) Edg. 



The disease is most common on old soils which have 

 been in cotton for many years. Unfavourable soil, 

 accompanied by an unfavourable season, results in a 

 heavy loss. The character and progress of the disease 

 varies greatly with the weather conditions. In most 

 cases the leaves turn yellow in irregular areas, producing 

 a mottled or mosaic effect, the parts next to the veins 

 being better nourished, retaining the green colour the 

 longest. Another condition is that in which a drought 

 is followed by warm rains. The mosaic condition is 



