CASSAVA CUCUMBERS 241 



CASSAVA 



The cassava of Jamaica suffers from a root rot 

 which is due to a fungus. The disease is most common 

 on plantations in new log clearings. On these clearings 

 there is a fungus which is quite common on the old 

 logs and stumps of the logwood, which has been 

 supposed to be the same as the one on the cassava, 

 but the connection has not been satisfactorily traced. 



CUCUMBERS AND MELONS, ETC. 



Very little is known of the diseases of these plants 

 in tropical countries, but many of the diseases reported 

 in the temperate zones doubtless occur in the tropics. 



Downy Mildew. This is a disease of the cucurbitace- 

 ous plants which is known in the United States and 

 Cuba, and is the chief cause of poor cucumber crops 

 in some localities. 



It is due to the fungus Plasmopora cubensis, 

 (B. & C.) Humphrey, which causes the leaves of the 

 diseased plants to show yellow spots with indefinite 

 outlines. In a short time the whole leaf becomes 

 shrivelled and dies. The disease starts with the oldest 

 leaves and works towards the tip of the vine. It can 

 be controlled by spraying with Bordeaux mixture. 



Water-melon Wilt. This disease is caused by a 

 variety of Necosmospora vasinfecta, E. F. Smith , which 

 is very closely related to the variety which attacks the 

 cotton (page 108). The character of the fungus and 

 the disease is very similar to what has been described 

 for cotton, and the remedy is practically the same. 



Other Diseases. The "damping-off " fungi Pytliium 

 De Baryanum, Hesse, and Corticium vagum, var. 

 solani, Burt, attack the cucurbitaceous plants. These 

 fungi are known to occur in the tropics, but have not 

 been reported on these plants. Other diseases of these 

 plants which may be reported from the tropics at any 

 time are the anthracnose caused by Colletotrichum 



R 



