46 



THE AGRICULTURAL NEWS. 



February 5, 1910. 



FUNGUS NOTES. 



CACAO DISEASES IN SURINAM. 



Two extremely interesting bulletins, numbers 20 and 21 

 liave recently been issued by the Department of Agriculture 

 in Surinam, dealing with diseases of cacao in that colon}-. 

 The main results are summarized in English, and it is from 

 the summaries that the following notes have been taken. 



c.vNKEE OR RED ROT DISEASE. The external symptoms 

 of this di.sease agree very closely with those described for the 

 stem and branch diseases of a similar nature which occur in 

 Ceylon, Java, the Antilles and the Canieroons. Consequently 

 it seems probable that the disease is the same in all these 

 countries. Mr. A. E. van Hall finds that the disease in 

 Surinam is due to a new species of Spicaria, which has been 

 named Spicaria colorans, and that a species of Nectria, very 

 probably Xectria striatospora, which is frequently found on 

 diseased trees, is only a harmless .saprophyte, and cannot be 

 regarded as being in any way the cause of the disease. This 

 is a conclusion of considerable interest to cacao growers in the 

 AVest Indies, as the canker disease found here has always 

 lieen attributed to two species of Keclria — Nectria theo'iromae, 

 and Cdlonectria Jlavida. But, as Jlr. van Hall remarks, the 

 parasitic nature of these fungi is not yet certain, and their 

 life-histories have not been fully worked out. The di-sease in 

 Ceylon and also in the Cameroons has always been attributed 

 to species of Kectria, but in both cases conclusive evidence is 

 wanting; it is therefore extremely probable that all these 

 fungi are only saprophytes, and that the true cause in 

 each case is really the fungus Spicaria colorans to which 

 the di.sease is due in Surinam. This last fungus produces 

 spores of a Fasarium form, as well as the Spiicuria form; but 

 no perithecia, or any other higher form of fructification were 

 ever formed in the artificial cultures. After carefully sifting 

 the evidence, ^Ir. van Hall comes to the further conclusion: 

 'I'p till now, there are no data which prove, or even make it 

 likely that the canker disease may attack the pods', though, 

 as will probably be remembered, species of Nertria have been 

 reported as causing pod diseases in Ceylon and elsewhere. 

 These conclusions serve to indicate very clearly that the true 

 cause of 'canker' disease of cacao in these islands, and the full 

 life-histories of the fungi JVecfria theohromae, and Cnlonectria 

 fiivida are points which still require very thorough and 

 critical investigation. The same is true of the diseases of 

 cacao pods. One other point of interest also arises in this 

 connexion. Owing to the semi-saprophytic character of the 

 fungi belonging to the genus N'ectria, it has always been 

 thought that canker disease originated in wounds indicted on 

 the bark. Should, however, the disease prove to be due to 

 Sjiicariii colorans, as in Surinam, there seems to be no 

 special reason why infection may not prove to be direct, 

 which would probably render the disease more ditticult to 

 prevent, though it would not alter the remedial measures 

 which should be adopted, once it has obtained a footing. 



DIE-BACK AND BROWN RiiT. These two diseases are 

 caused by the same fungus, which appears to be Biplodia 

 rncaoicola, the fungus responsible for the same diseases in 

 these islands. It was originally thought that the Surinam 

 disease was due to an allied genus, ChaetoJiplodin, \\hich 

 was separated from that of Diplodia on the ground that its 

 I'ycnidia were hairy while those of Biplodia were smooth. 

 This difference, however, was found to be due entirely to 

 .surrounding conditions and was not constant, for which 

 reason ^Messrs. van Hall and Drost suggest that the former 

 genus should be annulled. On some branches and pods the 



pycnidia appear in groups. This is a constant feature of the 

 stem form of the disease in these islands, and is the character 

 upon which the genus Zasiodiptodia was separated from 

 Biplodia. This character also was found not to be constant in 

 Surinam, and the Jlycologist to this Department has 

 observed the same thing to be true of specimens from these 

 islands. In consequence, it is suggested that the genus 

 Lasiodiplodia must also be abolished. 



It is further worthy of note that, for the same reason, 

 the two fungi Biplodia cocaoicola, causing die-back and 

 brown rot diseases, and that alluded to in the publications of 

 the Imperial Department of Agriculture as Lasiodiplodia sp., 

 fhould be regarded as one and the same fungus. Infection 

 experiments have not been undertaken here yet to prove this, 

 but the conclusion seems fairly reliable and has been sug- 

 gested independently by two French mycologists— Messrs 

 Griffon and Maublanc. These observers, however, suco-est 

 a different system of nomenclature, so that at present the 

 ultimate name of this fungus is in doubt. 



It is found in Surinam that the die-back disease only 

 affects trees that are in a leafless, or nearly leafless condition, 

 owing to thrips, wind effects, or sudden removal of shade. In 

 fact, as lias been recognized here, the fungus is only a facul- 

 tative parasite. It does not attack healthy pods, either, but 

 only those that have been injured, or affecled by other fungi. 

 In this connexion, evidence is accumulating which tends to 

 show that se\eral other fungi are possibly responsible for pod 

 diseases in the first instance; that is, they are capable of 

 attacking injured pods directly, and after the pods have been 

 weakened in this way, the brown rot fungus can obtain 

 a hold. It is possible that two or three species of Collefo- 

 trichum may be responsible for this direct attack, as mem- 

 bers of this genus are often found on cacao pods, and many 

 of the species are known to be vigorous parasites on several 

 different plants; an example is that causing cotton anthra- 

 cose, and another causing the witches' liroom disease of 

 cacao in Surinam. 



The remedial measures suggested are practically identi- 

 cal with those recommended for the same disease by the 

 Imperial Department of Agriculture, and need not be 

 repeated here. 



Some of the points mentioned above are of a distinctly 

 new nature and tend to overthrow some of the generally 

 accepted ideas in connexion with cacao diseases. It is 

 a peculiar fact that, in spite of at least ten years' work on 

 the subject in many parts of the tropical world, really 

 reliable and critical information on the identification and 

 life-histories of the fungi causing disease of cacao is only 

 now coming to hand. Even now, much work, particularly 

 on pod diseases and on the possible alternative host plants 

 of Diplodia racaoicola still remains to be done. 



Sporobolus Indicus. 



This grass is known in most, of the British West Indian 

 islands as 'hair grass' or 'bed grass.' In Martinique, it is called 

 'cabouya'; this name is also given there to Sporobolus Jaoiue- 

 inontii. In Guadeloupe, both S. indin,sa.nd S. Jacqtiemontii 

 are known as 'mabouge,' while the former has the additional 

 name 'malefoin.' 



.S'. j«A'c».s is a widely distributed plant. It grows welt 

 in dry places, and when young, forms good forage for sheep 

 and horses. 



.S. Jact/netiiontii is very closely related to S. indicus. 

 It is not as widely distributed, however, seeming to be con- 

 fined to Jamaica, Hayti and the French Islands. It has the 

 same natural habitat as S. indicus, but is not as abundant. 



