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DISEASES OF CROP-PLANTS 



This disease is more capable than anthracnose of withstanding 

 hot dry weather. 



Control. 



No fully effective means of control is known. The germs are 

 able to resist drying for a long period, and become widely spread, 

 so that probably reinfection does not entirely depend on seed. 

 The measures recommended for anthracnose should, however, 

 also reduce considerably the incidence of blight. 



Stem Rot. 



Bean plants raised in Barbados gardens from American seed 

 have several times been seen to develop brown decayed patches 

 on the young stems within the first two or three inches above 

 the soil. The injury extends deeply into the tissues and often 

 either girdles the stem or causes it to break. From the nature 

 of the mycelium found in the lesions the disease is believed to be 

 due to the soil fungus Rhizoctonia, which has been described 

 as the cause of stem rot of beans in the United States, and there 

 is a distinct possibility that the fungus is introduced with the 

 seed. Pods near the ground are said to be attacked by the 

 mycelium, which can enter maturing seeds without destroying 

 them. 



Seeds should be carefully picked over before planting, and 

 those which show even slight injury rejected. The disease can be 

 prevented to some extent by wide spacing and the avoidance of a 

 shaded condition of the soil. 



Pigeon Pea. 



Root and Stem Diseases. 



The pigeon pea [Cajanus indicus) is subject in the West Indies 

 to diseases, probably two or three in number at least, which 

 cause the death of the whole plant by infestation of roots, collar, 

 or lower stem. These are additional to the known susceptibility 

 of this plant to Rosellinia root disease. The occurrence of these 

 affections seems to be sporadic, though sometimes the losses are 

 fairly heavy. Their nature is at present almost entirely unknown. 



In 1917 old and young trees died off in large numbers but 

 in a scattered way in several districts of Carriacou, in the Grena- 

 dines, and a similar occurrence amongst young plants was seen 

 by the writer at a later date in the island of Bequia. In the 

 Carriacou material the disease is distinctly of the nature of a 

 stem and collar canker, and it is evident from the irregular 

 development of ribs of new wood about the lesions that it may be 

 present for a considerable time before killing the plant. The 

 only fungus found to be uniformly present is an Ascomycete 

 with dark hyphae giving a slaty appearance to the wood, pro- 



