328 DISEASES OF CROP-PLANTS 



Series) show a high degree of endurance of the disease, suggesting 

 that this character has influenced their selection. They become 

 generally but lightly infested, and make an apparently normal 

 growth. 



Perfect immunity exists, it would appear, only among canes of 

 the thin Indian type. The well-known Uba cane, the only one of 

 the type adopted in the West Indies, has been severely tested 

 without developing any symptoms of infection. The references 

 to " Kavangire " by Porto Rican and American writers on the 

 disease really apply, according to more recent information, to 

 Uba, introduced by way of the Argentine to Porto Rico. 



According to Brandes, corn, sorghum, rice, millet, crab- 

 grass, foxtail, and Panicum have been found to be subject to 

 infection, but are stated to be attacked with difficulty, con- 

 tracting the disease when grown in the close neighbourhood of 

 diseased cane. In Trinidad appearances strongly suggestive of 

 mosaic have been seen on corn and on so-called " corn-grass " 

 {Manisurus exaltata). 



Control. 



Uninfected regions should be protected by careful quarantine, 

 with special precautions against introduction on highly resistant 

 varieties, which may transmit the disease without showing signs 

 of infection in themselves. 



Light infestations may be dealt with by pulling up the affected 

 plants. There is no need to burn or otherwise destroy them 

 beyond taking precautions against the resumption of growth, as 

 wilted plants are no longer infective. 



Severe infestation should be dealt with by the thorough 

 clearing of the fields after crop, followed by the use of disease-free 

 material for replanting. If a rotation crop is interposed, the 

 security will be greater against reinfection from growing fragments 

 of the old stools. 



Chlorosis, Gall Patches, Moonshine. 



Chlorosis as known in the West Indies is a condition regularly 

 induced in cane planted on certain restricted patches in limestone 

 districts, in which the leaves become exceedingly pale in colour or 

 even milk-white. In addition to these permanent locations, the 

 condition may be manifested more or less over wider areas in wet 

 years. Chlorosis of this type is reported from Cuba, Jamaica and 

 Porto Rico ; it occurs to a small extent in Barbados, and is 

 particularly well-marked in Antigua, where the areas subject to it 

 are known as gall patches. H. A. Tempany has shown that the 

 condition is due in Antigua to the presence of soluble material, 

 indicated by analysis to be sodium carbonate (" black alkali "). 

 This is believed to originate from interaction between the calcium 

 carbonate of the soil and sodium chloride brought up in solution 



