332 DISEASES OF CROP-PLANTS 



A Jamaica disease resembling this in most particulars was 

 attributed by G. Massee in 1887 to a fungus named by him 

 Peronospora trichotoma. 



Control. 



Certain varieties are immune to the disease and may be 

 safely grown on infested land. Susceptible varieties should only be 

 planted on clean land, and care must be taken not to introduce 

 infection with the planting material or with instruments used in 

 cultivation. 



Fig. 139 Vasculomyces Xanthosomae 



Bull. 6, Dept. Agri., Jamaica 



In Jamaica and more recently in Hawaii a disease of Colocasia 

 sp. (taro) has been attributed to a species of Pythium. 



Arrowroot. 



Burning Disease (Rosellinia). 



In 1891 specimens of arrowroot rhizomes from St. Vincent 

 affected by a disease knowning as " burning " were examined by 

 H. Marshall Ward. They were reported by him to be badly 

 affected by a subterranean fungus mycelium, and to have pro- 

 duced conidia in the manner of the genus Spicaria when kept in a 

 damp chamber. 



No further outside attention seems to have been given to this 

 affection until South, after a visit in 1911, gave an account of it 

 in an unpublished report. He described the disease as occurring 

 in the fields in patches varying in area from a few to several 



