They are produced by a lack of vigour on the part of the 

 plant due to excess of water in the soil, or to the absence 

 of some essential element of plant food from the soil. 

 When a hot period, and a rainy one, succeeds a long 

 drought the progress of the disease becomes very rapid. 

 The leaves may fall or may adhere to the plant until the 

 fruit ripens. 



When the plant is thus weakened, fungi, which are 

 incapable of attacking it in a healthy condition, make their 

 appearance on the leaves. The fungi which occur most 

 commonly on these leaves are Sphczrella gossypina and its 

 conidial form Cercospora gossypina, Macrosporium 

 nigricantium and Alternaria sp. 



The treatment for this disease varies according to the 

 circumstances under which it occurs. If the disease is due 

 to an excess of water in the soil, a good drainage is to be 

 recommended. If, however, it is due to the absence of 

 some essential element of plant food from the soil, then 

 that element must be supplied in the form of a manure. 



The mosaic disease is well-known in the United States ; 

 a similar disease has been recorded in East Africa. 



ATKINSON : " Diseases of the Cotton Plant," U.S. 

 Dept. Agric. Bull. No. 33, 1896. 



RED LEAF BLIGHT OF COTTON. 



The foliage of the plant reddens like autumn colouring. 

 This is exceedingly common in healthy cotton towards 

 its maturity. It occurs, however, commonly on the 

 " upland " cotton in the United States when the plant 

 is young. In these districts the soil is poor. The bolls 

 produced are few in number and the leaves are shed early. 

 The disease is due to the absence of potash and nitrogen, 

 and probably phosphoric acid. 



The remedies consist in supplying the constituents which 

 are lacking. 



ATKINSON : " Diseases of the Cotton Plant," U. S. Dept. 

 Agric. Bull. No. 33, 1896. 



SHEDDING OF BOLLS. 



This occurs in the case of the cotton plant most 

 frequently in extremes of dry or hot weather, or during a 

 change from the one to the other. It may occur, how- 



60 



