September, 1009.] 



239 



Plant Sanitation. 



especially susceptible to this particular 

 form of attcak. All the young shoots 

 have been so persistently killed back 

 that the trees are actually dying- It is 

 proposed to coppice thern and, upon the 

 first siyns of a repetition of the attack, 

 to spray the young shoots with a soap 

 solution. 



The same trees, in their weakened con- 

 dition, have fallen an easy prey to the 

 brown boring catterpillar (Arbela qua- 

 drinotata). 



MISCELLANEA: CHIEFLY PATHO- 

 LOGICAL. 



By T. Petch, b.a., b. sc. 



In the Supplement to the Tropical 

 Agriculturist for May, 1909, it is stated 

 that Dr. Funk, of Apia, has discovered 

 a new parasitic disease which causes the 

 death of Cacao and Rubber trees. It 

 has been named Hymenochaite noxia, 

 Hennings. I have not been able to find 

 any further details of this. The descrip- 

 tion of Hymenoch&te noxia has ap- 

 parently not yet been published, and 

 therefore identification U impossible. 

 But it seems most probable that this 

 disease is our well-known "Brown Root 

 Disease." The latter is widely distri- 

 buted throughout the Tropics, and is 

 easily identified by its habit of cement- 

 ing sand, soil, and stones to the roots of 

 the trees attacked, by means of its 

 brown mycelium. But while any desired 

 number of specimens can be obtained, 

 these seldom show any approach to a 

 fructification. In one instance I was 

 able to examine three large Hevea trees 

 which had been killed by this disease at 

 intervals of two years ; the stump which 

 had been daad four years was almost 

 entirely destroyed by white ants ; that 

 which had died two years ago was well de- 

 cayed but not eaten away; but on neither 

 of these two, nor on the tree just dead, 

 was there any sign of a fructification. 

 Moreover, I have kept diseased stumps 

 under cultivation for four years with 

 equal lack of success. Under these cir- 

 cumstances, it is impossible to say what 

 the fungus really is. In the Report of 

 the Mycologist for 1905, it was referred 

 to Hymenoch&te, since one sometimes 

 finds bright brown patches, just above 

 the collar, which bear bristles resembl- 

 ing those of a Hymenochaite ; but, in the 

 light of further experience, I consider 

 this identification very doubtful. It 

 has been assigned to Hymenoch&te, iu 

 Samoa, where it attacks Cacao. But, iu 

 Java, Zimmermann considered that it 

 was a Sporotrichum, and named it 

 Sporotrichum radicicolum; there are 



sometimes tufts of branching hyphfe at 

 the collar, which resemble the conidio- 

 phores pf a Sporotrichum. According 

 to Ridley's description, the same fungus 

 occurs in the Straits. It is evident, 

 therefore, that "Brown Root Disease' 

 is common thoroughout the Tropics, and 

 it is most probable that the disease re- 

 corded from Apia is not a new disease, 

 but only a new name. Whether its dis- 

 coverer in Apia has been more fortunate 

 than others in obtaining an identifiable 

 fructification must reamin in doubt 

 until the description of the species has 

 been published. But so long as European 

 Mycologists are willing to give a name 

 to anything that is sent them, and do not 

 take the trouble to acquaint themselves 

 with what has been written on tropical 

 plant diseases, we may expect to be 

 periodically alarmed by reports of "new 

 diseases" which are merely the old 

 diseases under a new name. In Ceylon 

 "Brown Root Disease" attacks Tea, 

 Hevea, Castillua, Cacao, Caravonica, Cot- 

 ton, Camphor, and several species of 

 of ornamental shrubs ; it is practically 

 omnivorous. But it seldom spreads to 

 any extent, and, as a rule, the removal 

 of the affected tree and tbe addition of 

 lime to the hole effectually prevents 

 further loss. It is more easily controlled 

 than any other root disease we have in 

 Ceylon. 



In the Straits Agricultural Bulletin 

 for July, 1909, a disease of Hevea is re- 

 corded from Perak. The trees attacked 

 are about two years old. They die back 

 f com the tip, down to the base, if the 

 tree is not stumped below the diseased 

 part. A black fungus, with oval spores 

 transversely divided, is found in the 

 dead tissues. This appears to be identi- 

 cal with "Die back," which has been 

 known to occur in Ceylon since 1905, and 

 has been referred to on several occasions 

 in the Annual Reports. The fungus 

 which attacks the leading shoot is a 

 LUceosporium ; it turns the shoot brown 

 and soft, usually about the middle of its 

 length. Afterwards the shoot becomes 

 hard and grey, and the fungus produces 

 spores in minute pink or white masses. 

 According to my observations, this fun- 

 gus does not attack those parts of the 

 stem in which the wood is already formed; 

 but, after the death of the leading shoot, 

 other fungi grow on the dead tissue, and 

 these kill off the remainder of the tree. 

 The chief of these secondary fungi is 

 Botryodiplodia elastics; it forms black 

 patches in the bark, and tnese produce 

 large numbers of black, oval, transveisely 

 divided spores. There is not much doubt 

 that the fungus described in the Straits 

 Bulletin is Botryodiplodia elasticw, This 



