Ill 



DISEASES AND PESTS 



59 



direction with the prevailing wind, but the spores do not seem 

 to be carried great distances, as it has been observed that 

 patches of open land or low intervening hills can contribute 

 barriers affording protection to a considerable degree. 



Although air -currents are the principal agencies of dis- 

 tribution, no doubt exists that the disease can also be con- 

 veyed by insects. . . . Instances of infection by means of 

 insects are often found on diseased plantations, and to this 

 agency can be attributed isolated cases of the disease occurring 

 at considerable distances from infection centres. Such isolated 

 cases, if not properly treated, will soon develop into new 

 centres. 



The disease is spread by means of the two kinds of spores 

 produced by the fungus. In common with other members 

 of the genus Diplodia, it is a wound-parasite, i.e. effects its 

 entrance into the host through wounds. When a spore falls 

 on a cut or otherwise ruptured surface, it quickly germinates, 

 producing a mycelium which with great rapidity pushes its 

 way into the tissues of the host, and the first phase of the 

 disease is established. The disintegration and softening of 

 the tissues consequent on the growth of the fungus facilitate 

 the entry of the bacteria, which readily find the way to the 

 interior succulent parts filled with nutriment, wherein they 

 set up their destructive fermentation process. 



The most usual point of attack has been found to be the 

 " common pedicels " of the fruit clusters, into which the fungus 

 gains entrance through the wounds made when picking the 

 nuts. It is a well-known fact that this disease rarely attacks 

 palms not arrived at the age of bearing — and the reason is 

 very patent. Carefully conducted inoculation experiments in 

 the laboratory have established the fact of wound infection. 



Fredholm holds out no hope of saving any tree 

 known to be infected. Good cultivation is urged as 

 likely to make trees more resistant. The planter's 

 energy should be focussed on sanitation. " Burning by 

 some method or another " is advocated. Fredholm 

 seems to know from experience that burning completely 

 is not too easy. And it must be complete to have 

 any value. The more promptly it is done the better. 

 The trunk should not be split unless necessary, as it 

 burns. The use of lime is also suggested. A vigilant 

 watch for fresh outbreaks is urged, and it is noted that 



