238 



THE AGKICULTUEAL NEWS. 



July 15, 1916. 



PLANT DISEASES. 



PINK DISEASE IN THE WEST INDIES. 



Since the first description of pink disease by Zimmer- 

 mann (Java, 1901) a considerable amount of attention has 

 Ijeen given to it in the Eastern Tropics, especially since its 

 appearance as a somewhat serious enemy in plantations of 

 Hevea. Its range of hosts, both wild and cultivated, is an 

 extremely wide one, and under certain circumstances, it is 

 responsible for a considerable amount of damage. Its 

 presence on wild plants makes it difficult to eradicate from 

 estates bordering on forest. 



The disease causes the death of twigs and small 

 branches. Its most obvious characteristic is the production 

 of a fairly uniform pink coating on the surface of the bark. 

 And sometimes the leaves, of the aflfected parts while they 

 -are still alive, so that they appear as if they had been wcfll 

 dusted with carbolic tooth powder. Later the coating turns 

 grey and scales off. 



The fungus causing the disease in the East was des- 

 cribed as a new species under the name Corticium jaminicum 

 by Zimmermann, a name which was later changed to 

 C. Zimnierinanni. Further investigation showed its identity 

 with C. s(i iKonicolor, B. et Br., described from Ceylon in 

 1870, and this name having priority is now accepted. 



The occurrence of a closely similar disease in the West 

 Indies has been known from 1906, and several writers have 

 suggested that the New and Old World diseases might be 

 identical. At the instance of Dr. van Hall specimens were 

 sent "from this Office in 191.3 to Dr. Rant in Java, but no 

 information was received concerning them. 



The circumstances attending the discovery of pink 

 disease in the West Indies were as follows: — 



In 1906 ilr. Joseph Jones, Curator of the Botanic Gar- 

 dens, Dominica, forwarded to the office of this Department 

 diseased cacao twigs sent in by Mr. Sowray, who stated that 

 the disease caused the trees to die back considerably. An 

 appended note by Sir Daniel Morris, Imperial Commissioner, 

 says, 'This is the first time we have had authentic specimens 

 of the "pink" disease.' In the same year further specimens 

 on cacao were sent in by ilr. Bryant, and on lime by 

 Mr. Fletcher, the latter from an estate where the disease was 

 rediscovered on limes in 1911 by the writer. Specimens of 

 the fungus were reported by Kew to be immature and not 

 suitable for identification. In 1907 fresh material on cacao 

 was collected by the Curator, and forwarded to Kew. 

 A reply in the name of the Director was received to the 

 eftect that the fungus was Corticium lilacino-fuscum, 

 Berk. A: Curt., and this name has been in general use in 

 the West Indies until recently. Specimens showing the 

 disease were forwarded from St. Tjucia later in the same year, 

 and it has since been recorded from Trinidad and Porto Eico. 



At no time has it appeared as more than a local trouble, 

 and material for study has been difficult to obtain. At the 

 instance of Dr. Butler, Imperial Mycologist for India, 

 Mr. .1. B. Itorcr, Mycologist to the Board of Agriculture, 

 Trinidad, has recently collected specimens on cacao in Trinidad, 

 which were submitted to Kew and examined by Miss E. M. 

 Wakefield, while further specimens, together with material 

 of the di.'^casc on limes in Dominica supplied through this 

 1 )cpartment, were examined by Professor Burt of the Missouri 

 P>otanical Gardens, .an authority on the group. Mr. Rorer 

 has now published the replies received, together with an 

 account of the disea.se, in the Bulletin of the Department of 

 Afjriadmre, Trinidad and Tobago, Vol. XV, Part 3. 



Miss Wakefield reported as follows: — 



'The specimens of West Indian "Pink Disease" forwarded 

 by Mr. Rorer are wrongly determined as Corticium lihicino- 

 fasrum. I have compared them with I'orticium salmonicol- 

 or, B. et Br , and consider that they should be referred to 

 this species. 



'The West Indian specimens do not show the characteris- 

 tic cracking of the hymenium quite so plainly as is usually 

 the case in the Eastern forms, but in some of the specimens 

 it is quite evident under the lens. No Necator stage is 

 present in this material. 



'With regard to the spore difference noted by Mr. liorer 

 in his letter to Dr. Butler, the spores are somewhat variable 

 in width, but I have rarely seen them quite so nanow as 

 Zimmermann figures and describes. They are usually more 

 or less broadly pip-shaped or obovate. 



'The spores resemble those of C. roseum, Pers., but this 

 species differs from C roxeiim in its less fleshy consistency, 

 and in the much broader basal hyphae ' 



Professor Burt reported: — 



"With regard to the pink disease, the specimens from 

 Dominica (on lime) do not differ with regard to the fungus 

 from the specimen which you have sent from Trinidad (on 

 cacao). It seems that the pink disease is very probably 

 caused by the same species of Corticium in both the Eastern 

 Hemisphere and the Western. Yours is not caused by 

 Corticium lilariiK t-fuscum. 



'During the latter part of December, I received from 

 Kew Herbarium, a specimen of Corticium salmonicotor, B. 

 and Br., collected in Ceylon by T. Petch, which agrees 

 exactly in colour, cracked habit, and all structural details 

 with the specimens of "pink disease fungus" which you sent 

 me. A fragment of the authentic specimen of Corticium sal- 

 monicoloi' from Ceylon, determined by Berkeley, was also 

 .sent to me. Sectional preparations from this specimen are 

 of exactly the same structure, spores, etc., as Petch's speci- 

 mens and your collections. 



'Miss Wakefield writes to me that she has studied the 

 specimens which you sent to Kew and compared them with 

 the Ceylon miterial of Corticium salmonicolor, and believes 

 your specimens to be C. salmonicolor. I agree with her. 

 Corticium roseum is the next thing to C. salmonicolor, but it 

 has bushy branched paraphyses between the basidia; these 

 paraphy.ses are often very conspicuous. I have found no 

 paraphyses of this sort in the "pink disease fungus." The 

 absence of these paraphyses and the coarser hyphae of 

 C. salmonicolor, and the fact that C. roseum is strictl}- sa])ro- 

 phytic, wherever observed, show that these two fungi are 

 distinct species." 



There is thus no room for doubt that the West Indian 

 disease is identical with that in the East. There was only 

 one point left outstanding in this connexion, i.e., as to the 

 identity of the jiarticular specimen sent to Kew in 1907. 

 A portion of the same material is still preserved here, and 

 a comparison of this with dujilicate material of that supplied 

 to I\rr. Rorer shows no point of difference. 



That this disease has not assumed in the West Indies 

 anything like the importance it has in the East would appear 

 to be due to differences in climate. The fungus is dependent 

 on a very considerable amount of moisture for vigorous 

 growth. Even in Dominica and St Lucia, the wettest of the 

 Lesser Antilles, there are few places opened up to cultivation 

 which are not penetrated morer or less by wind and sun all 

 the year round: it is notable that the disease on the lime in 

 Dominica is only known to exist in one specially sheltered 

 situation, although it was recorded from the same estate ten 



