Plant Sanitation. 



22 



[Jan. 1908. 



line of demarcation will be noticed between the diseased petioles and the healthy 

 bud. This mycelium cuts off much food to and from the leaf, and therefore assists 

 in the general disorganization of the functions of several parts of the plant. 



The general opinion of the planters of coconuts was that this disease is due 

 to the weakness of the plants produced by the setting of immature nuts. In some 

 districts histories of weather-beaten cargoes of green nuts been driven on the shores 

 and the nuts used for planting purposes were held out as the cause of the trouble. 

 This disease, however, is not limited to a few scattered trees, and evidence distinctly 

 points to its being infectious. A tree that has become attacked by the disease is 

 sooner or later surrounded by a large number of others showing signs of the disease. 

 In one portion of the Cedros district, the disease has been noticed making its way 

 gradually into other fields of coconut further South. It is, therefore, impossible 

 to believe that the large ar3as of coconuts in Cocorite, Laventille, Guapo, Cedros, 

 and the interlands of Mayaro were planted with immature nuts. 



Moreover, the fungus found in the roots and in the petioles of diseased 

 trees is capable of attacking vigorous trees ; but anything which tended to reduce 

 their vitality would considerably help along the fungus. Circumstances which 

 retard growth, both of the root and shoot system, give the root fungus a much 

 better chance. This was conspicuously brought to my notice on a portion of an 

 estate in the Cedros district. A low-lying hollow showed that a large quantity of 

 water was present in the soil. Such a condition was unfavourable to good develop- 

 ment of the trees ; they were stunted in growth and showed that root development 

 was not very large. The clayey impervious nature of the soil suggested that an 

 elaborate system of drainage was needed in order to procure the aeration necessary 

 for vigorous plant growth. In this hollow most of the trees had died out very 

 rapidly, and the disease had soon spread from this portion of the estate to other 

 parts where the soil conditions were very much more favourable. Trees on sandy soil 

 on higher ridges were often noticed to be attacked, but it is generally in low-lying 

 undrained hollows that the disease is the worst. This is also seen in the Guapo and 

 Mayaro districts. 



These examples should suffice to show how natural peculiarities of an estate 

 and other physical features affect the disease, but these alone cannot be sufficient to 

 cause the death of the trees, as is often urged. The characters of the soil affect the 

 growth of the plant, and they may also affect the fungus, and therefore it is necess- 

 ary to keep the condition of the soil as good as possible, in order that it may be 

 favourable to the growth of the plant. 



It is also commonly stated that lack of cultivation and manuring is the 

 -•ause of the trouble, and it should not be forgotten that every effort to improve the 

 condition of the soil and render it better adapted to the healthy and vigorous 

 growth of the root system may be a blow at the fungus, for some of the new roots 

 would certainly go to replace those destroyed by the parasite. 



The presence of a parasitic fungus in the roots and in the petioles must, 

 therefore, be held to be the cause of the disease, and improvements in cultivation, 

 drainage, manuring, etc., should be practised as they possibly may affect the 

 disease indirectly by rendering the coconut plants more capable of withstanding 

 its attacks. 



The distribution of this disease apears to be fairly general throughout the 

 coconut districts, and considerable loss has been experienced in the southern end 

 of the island. 



The aggregate injury throughout the colony must be very considerable, but 

 it is only in a few localities that serious loss has been experienced. 



