CHAPTER XXV 



DISEASES OF COTTON 



Internal Boll Disease 



The internal boll disease of cotton is a special case, and was the 

 first to be studied, of a type of parasitic disease (stigmatomycosis), 

 in which certain specific fungi are conveyed by plant-feeding 

 bugs, and gain access to the interior of the fruit by means of the 

 punctures which the insect makes in feeding. Similar affections 

 have lately been found to be of very wide distribution in the West 

 Indies and to affect the fruits or seeds of a great variety of 

 plants. (See p. 29.) 



In the cotton boll the fungus so introduced develops freely on 

 the immature lint, which may be thus completely rotted or more 

 or less severely discoloured, according to the stage of development 

 reached when infection takes place. The seeds may or may not 

 be infested. 



There is in addition, a bacterial form of the disease, in which 

 infection similarly takes place through bug punctures, but in 

 regard to this it has not been demonstrated whether the invading 

 organism is actually conveyed by the bug or only enters from the 

 surface of the boll by way of the passage provided by the puncture. 

 This form of infection has not been noted on plants other than 

 cotton. 



History and Distribution. 



The nature of the disease was not discovered until 1914, but 

 effects undoubtedly attributable to it have been reported from 

 time to time since the revival of cotton-growing in these islands 

 in 1902-3. The greater part of the damage done, especially the 

 recurrent heavy loss in St. Vincent, was attributed to other 

 causes. 



Since 1914, the disease has been verified by the writer as 

 existing in Tortola, St. Kitts, Nevis, Antigua, Montserrat, St. 

 Vincent, Barbados, Grenada and Trinidad. It was indepen- 

 dently discovered by S. F. Ashby, in Jamaica, in 19 15, and a 

 reference to fungi found in cotton bolls by A. W. Bartlett shows 

 unmistakably that it occurred in British Guiana in 1907. Its 

 prevalence is closely associated with that of its principal carriers, 

 the cotton stainers [Dysdercus spp.) and the green bug {Nezara 

 viridula), of which the former are by far the more important. 

 263 



