i86 DISEASES OF CROP-PLANTS 



In the case of trees which are attacked in the region of the 

 central bud there is no hope of remedy, but some success has 

 been attained in the treatment of cases where the infection is 

 situated in the outer parts of the crown. One kind of treatment 

 commonly adopted consists in setting fire, if necessary with the 

 aid of kerosene, to the dry material present in the crown. This 

 may give the tree a severe check but is sometimes successful in 

 destroying the infection owing to the shallow penetration of the 

 rot on the harder parts of the tree. 



A method sometimes adopted, which is claimed, with what 

 justification is not known, to prevent infection and to cure 

 incipient cases is the tying of a bag containing a pound or two of 

 coarse salt or of copper sulphate, or both, in such a position that 

 rain water will gradually dissolve the chemical and carry it down 

 among the leaf bases. 



Spraying with Bordeaux mixtiu^e, to which arsenate of lead 

 is added to give it insecticidal properties, has been experimen- 

 tally tried in Trinidad with apparently good results. The bud- 

 rot of palmyra palms in India has been successfully treated on a 

 large scale by spraying with resin-soap Bordeaux, applied by 

 climbers furnished with auto-sprayers, after removing infested 

 leaf -sheaths. 



In the destruction of diseased trees by fire they should be 

 cut down, the dry material used to start the fire, and the crown 

 dismembered and thrown on piece by piece, care being taken to 

 see that everything is at least scorched through. Excepting its 

 uppermost section there is no need to burn the trunk. 



Bud-Rot caused by Phytophthora palmivora. 

 Incidence. 



S. F. Ashby has described a specific bud-rot which occurs in 

 the eastern and north-eastern coastal lands of Jamaica, where 

 there are large unbroken areas of coconuts subject to a rainfall 

 of 90-120 inches. It is to a marked degree most prevalent on 

 flat lands with fine silt soils difiicult to drain. Periods of heavy 

 rain are followed one to three months later by a heavy increase 

 in losses from the disease, which in one instance of a field of 

 4,000 trees occurred at the rate of 100 a month. Trees from 

 2-3 up to 20 years old are liable to attack. On one estate the 

 fungus was found associated with the dropping of full-grown 

 immature nuts, and at one nursery seedlings were seen with dead 

 hearts and rotted apices probably due to infection from the husks. 



Symptoms. 



The existence of the disease is indicated by the discoloration 

 and withering of the heart leaf or one or more of the youngest 

 leaves. The heart leaf rots at the base and can usually be pulled 

 out, which serves as a rough means of distinguishing this affection 



