INSTITUTE, PUSA, FOR 1917-18 7? 



obtained during the past year in the fungus observation 

 plots at Rajabhatkhawa show a number of new attacks but 

 a relatively low proportion of fresh deaths. 



(4) Black thread disease of rubber. In Burma 



there is now hardly a plantation in bearing that is free 

 from the effects of this disease. It is not confined to the 

 tapping surface and the fruits as previously supposed, but 

 it attacks leaves as well and causes an extensive defoliation. 

 The infected trees do not readily recover from the effects of 

 leaf-fall and consequently there is a great reduction in the 

 yield of latex in the months of October, November and 

 December when under normal conditions the trees are 

 expected to yield their maximum, before natural wintering 

 takes place. 



The remedial measures previously recommended have 

 been tested on a plantation scale in Burma and have been 

 found to be successful. The removal of seeds and the free 

 admission of light and air by thinning and pruning have 

 proved effective in reducing both leaf-fall and black 

 thread on the tapping surface; but on account of the high 

 cost of systematically removing the seeds it is doubtful if 

 this measure is commercially practicable. In the Federated 

 Malay States a regular application of Izal on the tapping 

 cut has proved effective in preventing and checking black 

 thread, but on a plantation m Burma where this disinfect- 

 ant and others, such as, Solignum and Brunolinum, were 

 given an extensive trial they have not been found to do 

 much good ; the reason is that in Burma there is more likeli- 

 hood of the disinfectant being washed off in the more fre- 

 quent heavy showers of rain than in the Federated Malay 

 States where the rainfall is not as high as in Burma and is 

 not confined to four months of the year. 



The extent of the damage done by black thread on differ- 

 ent plantations in Burma is not the same. The varying 

 amounts of rainfall in the different rubber growing dis- 

 tricts do not seem to have any direct bearing on the extent 

 of the disease on the tapping cut, and on the amount of 



