30 



THE AGItlcri.Tni.VL NEWS. 



.Km un 16, 191"). 



FUNGUS NOTES. 



COCO-NUT AND CACAO DISEASES. 



A general review ol Professor Copeland's recent 1 k on 



the < loco nut, published in Messrs. Macmillan's series of mono 

 graphs on tropica] agriculture, appeared in the last number of 

 this journal, and a review of Dr. van Hall's work on cacao 

 in the same series appears on another page in the present 



issue. Each 1 k contains a summar} of present know] 



edge regarding the diseases of the plant which forms its 

 subject, and these are of interest as affording a view of these 

 diseases in broader perspective than is found in depart 

 mental publications. 



The diseases oi the coco-nut discussed in Copland's 

 summary are five in number. The stem bleeding disease, due 

 to Thielaviopsis, is known in Ceylon, India and Trinidad, 

 but appears to !»■ regarded as serious only in the first named 

 place. Apparently the author is not aware that T. et/oaceticus 

 i- a sj iM ■ 1 1 \ in of T.paradoxa. 



The leaf disease caused by Pestalozzia palmarum is 

 quite general in its distribution. Only in isolated instances 

 however, has it been reported as causing a serious epidemic, 

 and its usual position is that of a weak parasite, only 

 capable of advancing when the tree is weakened from some 

 other cause. 



The author refer- to this fungus as the cause oi a leaf 

 disease, but in the West Indies it is known t<. produce 

 a disease of the petiole also. 



Evidence as to the existence of a specific disease due 

 to Diplodia is given, but it is conflicting, and obviously in 

 need of confirmation. 



There remain the Imd mts, which are adequately dis 



c USSed. The evidence On this subject has inure than once 



been reviewed in this journal, so that we need not follow the 

 author in his summary of it. He recounts, however, his own 

 experience in combating an epidemic in Luzon, in the 

 Philippines, which is inten sting as a record of an attempt to 

 put the usual recommendation as to the use of fire into vigo- 

 rous practice, The di.-ea-e hnd existed for many years. In 

 the badly infested districts there were patches where almost 



every tree Was smitten, and larger areas where fully half 



the trees were dead or dying. The presence of a moist 



at sphere was found to be the predisposing cause of the 



disease. Legislation was secured making the disease noti 

 liable, and requiring, under penalty of fine or imprisonment, 

 the destruction bj fire of the crowns of affected tree-. Three 

 months after the campaign began (October 1908), a di d 

 tree had become an uncommon sight, and the new cases 

 ,M ing were less than one-tenth as numerous as they had 

 been one yi In 1913 the disease was still appeal 



,iit very scantily, and at the present time is practically 

 harmles The author's concl io ■ (l> that the best 



i fighting bud rot is the destruction of the sources of 

 infection, and (2) that attempt to save infected trees an at 

 best •' waste of t 



Tin- diseases i I i icao have been the subject ol so much 

 discussion that van Ball's opening remarks to the effect that 

 theii number is comparatively -mall is somewhat arresting. 

 [ts justification is seen, however, when we consider the effect 



which recent research has had. of reducing to the rank of 



saprophytes a large number oi the fungi previously held to 

 be parasitic, and the unification oi other- which had been 

 regarded a- distinct species. Thus the Nectrias are not even 



mentioned in tie t< a. and tl nee complex I liplodia group 



is combined under Diplodia cacaoicola. a name which tie 

 author has preferred to Bancroft's Thyridai'ia tarda, on the 

 ground of popular usage. 



The author still regards die-back due to this fungus as- 

 .i serious disease, but agree- with recent opinion that this 

 is only the case where entrj is afforded by wounds or 



unhealthy ndition of the twig-, such as may he brought 



about by exposure. There is no doubt in the reviewei - mind 

 that a very considerable amount of the damage -till attribu- 

 ted to tin- disea-e i- due to root troubles, or to the effects of 

 wind or -un. The author is further doubtful as to the exis- 

 tence ot a specific pod rot due to Diplodia (tic 'brown rot' 

 of West Indian writers), and in his experience ha- found 



it possible to prove that most of the pod- bearing the fungus 



had first been attacked by Phytophthora. Nor doe- he accept 

 the existence of a Diplodia (Thyridaria ) root disease as estab- 

 lished. His mention of the black root disci-.- due to 

 Roselliiiia sp. must seem inadequate to anyone who has 

 seen the very definite specific characters it displays in the 

 Held. It is true that its nature has not been established 

 according to the rigid rules of proof — the same can be said 

 of most root diseases of tree- but the manner of its spread 

 and the constancy of its characters are decided!) convincing. 

 With regard to canker, the author states as a remarkable 



fact that the blackening of pods, and the canker of the stem 

 and main branches db not at all occur side by side in the 

 cacao fields, and instances that in -lava several plantations 

 suffer badly everj year from canker, whereas black rot 

 of pods is alnio-t an unknown thing: conversely, in 

 Kamerun, black rot is most serious, but canker is of QO great 

 importance. While accepting the current view that canker 

 i- due to Phytophthora, he lays stress on the great intlii. 

 of cultural condition- on it- incidence. 



We turn with especial interest to the section dealing 



with the Surinam witch I. room disease, attributed by the 

 author to Colletotrkhuiit luxificum, a connexion recently 

 questioned by Rorer. The disease probably arose in the 

 Surinam plantations by transfer from Theobroma speciosum 



which grows wild in the south ot Surinam, and in the i 



of the Amazon in Brazil. 



The actual damage does not arise from the formation of 



the hypertrophied twigs from which the disease derives its 



name, but from the infection of tie- Cushions, on which 

 Crowded and useless hlossoms are then produced, and of I In 



pods, which become hardened, and contain beans which an 



lirowned and spoiled. In this way the disease is said to be 



responsible forlosses which maj amount to nine tenth- of tin 

 normal crop. 



Tie- method oi control adopted consists in removing and 

 burning all the leaf-bearing branches, treating the wounds 

 with tar, and spraying the remaining parts of the tree with 

 3 per cent, coppei mlphate solution. It has been demonstrat- 

 ed that by this mean the disease can bi effectively controlled^ 

 though a watch ha- .-till to l„ maintained for fresh out- 

 breaks, and pi tarj spraying with Bordeaux mixture 

 at h asl once a yeai i- advisable, 



