COTTON 113 



under side of the leaf. A little later in the season, the 

 formation of the conidiophores on the under surface 

 gives the white frosty effect. It is most common on 

 cotton growing in low, moist land, and causes a 

 premature falling of the leaves. In general it does not 

 do much damage, but occasionally causes considerable 

 loss by reducing the leaf surface of the plant. It is 

 common in the United States and in the West Indies, 

 and has been reported from the Transvaal. 



Angular Leaf -Spot. Clear watery spots are some- 

 times formed at the angles of the veins or along the 

 sides of the large veins and ribs. These spots contain 

 millions of bacteria, but there is some difference of 

 opinion as to whether the disease is due to the bacteria 

 or is a physiological condition which has been taken 

 advantage of by these organisms. As the disease 

 advances the tissues become dry and dead and 

 frequently break into holes. 



Cotton Boll Rot. This is a disease which causes 

 considerable loss by rotting the unripe bolls. It has been 

 known in the United States since the earlier part of the 

 last century, but its cause is as yet not fully decided 

 upon. Stedman made a study of it and attributed the 

 cause to a bacterium which he described under the 

 name Bacillus gossypina, but his results have not been 

 fully confirmed. It works on the strongest plants and 

 in the richest land, and is most severe during wet 

 weather. 



In 1897 Professor C. F. Baker made some studies 

 of this disease in Alabama, and came to the conclusion 

 that the primary cause was one of the small leaf-hoppers, 

 commonly known in the Southern United States as 

 " sharp-shooters." These little insects not only cause 

 injuries by puncturing the bolls but they facilitate the 

 entrance of numerous fungi. Professor Baker's investi- 

 gation demonstrates the presence of three species of 

 Bacillus, and Colletotrichum gossypii, Fusarium sp., 

 Altenaria sp., Rliinotriclium macrosporum, Farlow, and 

 R. tenellum, B. & C. 



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