and Magazine of the Ceylon Agricultural Society. 



267 



ingrowths from the surrounding living bark pro- 

 duce a " canker." Instances of such cankers 

 can be found on twigs one-tenth of an inch in 

 diameter; and, as far as is known at present, 

 "Corticium javanicum" is the only fungus which 

 produces " branch canker " on branches less 

 than half-an-inch in diameter. The dead bark 

 is not cast off; it remains within the canker, 

 ragged and fibrous on the younger twigs, or 

 smooth and blackened internally on the larger. 

 As a rule, the pink fungus tissue dies during the 

 dry weather and disappears, but examination 

 with a hand lens will generally reveal minute 

 patches still adhering to the dead bark. There 

 is no danger of any further infection from these 

 cankers when the pink tissue has disappeared ; 

 the branches should be cut off and burnt when 

 they are covered with the fungus. All the evi- 

 dence points not to a continuous infection from 

 the cankered branches, but to a re-infection from 

 external sources during each monsoon. 



Examples on the older branches of tea from 

 other estates show that the 



FUNGUS GROWS ON THE UPPER SURFACE 



of these and kills the bark over a comparatively 

 small area. When the fungus ceases to grow, 

 the ingrowth of a swollen margin from the 

 surrounding healthy tissue takes place as before, 

 resulting in the formation of the typical branch 

 canker of thick branches. The dead bark per- 

 sists for some time within the canker, and 

 often shows the superficial fungus patch, gen- 

 erally bleached white. If the bush is vigorous, 

 the wound may heal over completely, and ex- 

 perience proves that an excess of potash in the 

 manure applied is of great assistance in pro- 

 moting this recovery. But in most cases water 

 lodges in the wound and induces decay, while 

 fungi, otherwise harmless, grow on the dead 

 bark and wood and assist in the gradual 

 hollowing out of the branch. 



The commonest saprophytic fungus in such 

 situations is "Hirneola polytricha, ' Mont. This 

 occurs in abundance on dead wood all over the 

 Island, and naturally the dead wood in the 

 branch canker does not escape. It does not, as 

 a rule, produce any fructification when growing 

 in these cankers, but that can readily be induced 

 to grow from them under suitable conditions in 

 the laboratory. The fructification is circular, 

 either flat or cup-shaped, sometimes on a short 

 stalk, sometimes sessile ; the upper surface 

 is bluish purple or violet, usually with a 

 whitish bloom; the under surface and stalk 

 are covered with closo set white hairs ; it 

 differs from most of our common fungi in its 

 consistency, being midway between leathery and 

 gelatinous ; internally it has the same colour as 

 the upper surface. The white strands, one form 

 of "Thread Blight," which are often seen issuing 

 from the canker and spreading over the healthy 

 tissue, are the mycelium of this fungus. The 

 description of this species is inserted here merely 

 as a matter of interest ; the fungus does not cause 

 branch canker, and its white mycelium spreading 

 from the decayed tissue does no damage. There 

 are, of course, other forms of " Thread Blight," 

 many of which cause serious damage, but in 

 Ceylon the dangerous parasitic species have 

 not been found except on nutmeg and junglo 



trees. The " Thread Blight " which grows from 

 a branch canker is, as far as is known at pre- 

 sent, harmless. 



It must be borne in mind that the branch 

 canker here described begins with the killing of 

 the bark by " Corticium javanicum," and that 

 when this fungus has disappeared, as it does, 

 there is no danger of further infection from that 

 particular wound. The subsequent decay of the 

 wood is in a great measure caused by rain, &c., 

 though it may be assisted by saprophytic fungi. 

 It is not necessary, therefore, to cut off all 

 the cankered branches, since, as a rule, they are 

 not noticed until long after the cause has dis- 

 appeared. In many cases badly cankered fields 

 yield a large crop (up to 1,000 lb per acre) and 

 it would be absurd to sacrifice this unless there 

 was grave danger of infecting other fields, it 

 would be quite sufficient to tar the wounds in 

 order to arrest further decay. 



The above account of branch canker is appli- 

 cable to the majority of cases on estates at 

 an elevation of more than 4,000 feet. In the 

 neighbourhood of Peradeniya, branch canker 

 is caused by quite a different fungus, a speciea 

 of "Physalospora'' which kills the bark. But 

 even here it appears that the fungus is only 

 concerned in the initiation of the canker, and is 

 not present in the hollowed stems. In other 

 districts, what is known as branch canker is 

 frequently the result of white ants following 

 shot-hole borer, and the treatment in these cases 

 must deal with the latter. 



General. 



The periodic infection of tea and rubber during 

 the south-west monsoon points to an influx of 

 spores of the fungus from some external source 

 during that period. The fungus has been found 

 in the jungle on bushes, and the fact that the 

 worst affected tea estate is surrounded by jungle 

 on three sides tends to confirm the view that the 

 spores are blown from there. There is no doubt 

 that we are dealing with a native, not an intro- 

 duced fungus. 



Mr. Kidley states that the "Corticium'' so com- 

 mon in the Straits on Ramie and"Strobilanthes," 

 when overcrowded and too damp, is probably 

 this species. It has been found in Ceylon on 

 "Hevea brasiliensis," (tea up-country;, plum (up- 

 country), orange (low-country), and cinchona. 

 In Java, where the disease is known as " Dja- 

 moer Oepas,'' it attacks coffee, ramie, cacao, 

 cinchona, nutmeg, tea, " Eriodendron," pepper, 

 coca, cinnamon, kola, "Castilloa elastica, Hovea 

 brasiliensis," dadap, "Bixaorellana," mango, and 

 many other trees or shrubs of minor importance. 



It has been suggested that the " cankers " 

 previously described on Hevea and cacao, 

 as well as the undescribed Ceylon canker on 

 cinchona, are all caused by " Corticium java- 

 nicum." But in the original " cankers '' of 

 Hevea, cacao, and cincona, the diseased bark 

 is moist, whereas, when killed by "Corticium," 

 the bark is dry. This difference indicates a 

 totally different agent in the two cases. 



T. Petoh, 

 Government Mycologist, 



Juno 25, 1909. 

 — R. B, Gardens Circular, 



