3^3 



to another. Seedling rubbers do not seem to be attacked by this 

 fungus if left in the infected ground, but I would not advise an im- 

 mediate replant. It would be better to fallow the infected ground, or 

 as I have suggested to run bananas or some such plant through the 

 spot to clean it up. 



Diplodia. 



I will now say a few words about the more troublesome fungus 

 Diplodia. This pest has been called Dieback, but as I am by no nucans 

 certain that all the diseases here and in Ceylon which have been called 

 Dieback are the same thing for fear of mistakes I prefer to use the 

 scientific name of Diplodia which, unlike many scientific names, is easy 

 to pronounce and remember. This fungus is very small and incons- 

 picuous. Its spores are very minute and produced in immense abun- 

 dance after rain. When these spores reach a wounded rubber tree, 

 they germinate in twelve hours, putting out a minute thread which 

 enters the cambium layer and commences to grow. It generally, if 

 not always, attacks a cut or broken shoot and descending kills the 

 cambium layer. The growth is rapid and it has been known to kill a 

 four year old tree in about three weeks after its first being noticed. All 

 that is visible at first is that the top of the branch is dead ; it generally 

 exudes a little latex which runs down and turning black makes fairly 

 conspicuous streaks, but this is not always visible. On the bark are 

 to be seen little raised pustules with a crack across the centre, these 

 are black within. As soon as rain falls the fruit ripens and a substance 

 like soot appears in strings and irregular masses, from these pustules. 

 This substance consists of myriads of minute spores, elliptic and 

 divided transversely in two and black in colour. In the case of a 

 seedling the disease pushes down the stem killing it as it goes, but in 

 a strong plant, its course is checked. The seedling throws out a 

 beed, below the dead and dying end, the disease stops and the dead 

 portion falls off. You will see at once the danger of this pest. It 

 starts almost out of sight in big trees, at the end of a shoot, it is 

 difficult to get at, it is readily dispersed to great distances by the wind, 

 its spores are produced in unusually large amount, and it is very 

 rapid in growth and development. 



When detected it can be checked by cutting off the infected 

 bough and burning it, at the same time spraying liberally with bor- 

 deaux mixture. Still a tree may be badly injured and at least its 

 output of latex restricted by the necessary amputation. However, in 

 carefully watched plantations the injury may be minimised. But are 

 all plantations carefully watched.'' Para rubber is planted all over 

 the country by all sorts of people, little patches of half a dozen trees 

 here and there, native plantations which the owner perhaps hardly 

 looks at once a week, and then only cursorily. Any one will see that 

 a patch of trees may be infected, neglected, and form a focus for the 

 dispersal of spores in every direction. One large-sized badly infccird 

 -tree could produce enough spores to thoroughly infect a large area. 

 It rs to this dangei that 1 would call your attention. Rapid as is ths 



