PHYTOPHTHORA SP. Ox\ HEVEA BRASILIEXSIS. 



JEHAXGIR FAEDUXJI DASTUR, B.Sc, 

 First Assistant to the Imperial Mycologist. 



IXTRODUCTIOX. 



A POPULAR account of the disease of Hevea stem and fruit known in 

 Burma as "' Black Thread " and caused by a Phytophthora has been published 

 by the Burma Department of Agricultuie.^ It is therefoie not necessary in 

 this paper to discuss the macroscopic characters of this disease. 



The •'' Black Thread '"' disease first attracted the attention of the Burma 

 Rubber Planters five or six years ago when the disease became very prominent 

 by the damage it did on the tapping area. However it seems to be of a loncrer 

 standing in Burma, at least on the fruits. As far back as 1905 specimens of 

 diseased Hecea fruits from Mergui were sent to the Imperial Mycologist for 

 examination, and in 1906 the Manager of the Rubber Plantation, Mergui, wrote 

 that it was the fourth year the fruits in the garden had been attacked but 

 that in no case had the disease been noticed on any other part of the tree except 

 the fruit. They were at that time supposed to be attacked by a Nectria ; but 

 specimens of these diseased fruits sent in 1905 from Mergui have been examined 

 by me and they show not only the presence of Nectria but also the resting 

 conidia of a Phytoph.thora similar to those found by me in Burma in 1915. 

 It is therefore reasonable to conclude that the disease of the fruits caused by 

 a PhytophtJwra has been present in Burma at least since 1903 ; whether the 

 disease on the tapping area is as old as this it is difficidt to say. 



^IlCPvOSCOPIC ChaPvACTEES. 



Sections through diseased tapping areas show the cell walls turned brown 

 or yellow and in some cases swollen and the cell contents destroyed. At 

 times the stratification of the swollen cell wall appears very distinctly. The 



I Dastnr, J. F. Black Thread Disease of Hev^a in Burma. Dept. Agr.; Burma. Bull. 

 No. 14. 1916. 



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