2S6 



THE AGRICULTURAL NEWS. 



August 30, 1913. 



FUNGUS NOTES. 



MYCOLOGIOAL WORK IN SOUTHERN 

 NIGERIA. 



A considerable part of the Annual Keport on the 

 Agricultural Department for Southern Nigeria, 19r2, is 

 devoted to an account of the field investigations conducted 

 in the Protectorate during the past year by the Government 

 Mycologist, Mr. G. (). Farquharson, M.A., B.Sc. 



It is observed, first of all, that the fungus flora so far 

 examined of economic plants in Southern Nigeria is very 

 similar to that of Southern India, Ceylon, Malaya, Java and 

 the East generally. 



RUBBEl: DISE.\SES. 



The most important diseases attacking ruliber trees 

 appear to be Fomes semitosius, Berk , and Ilymenocheate noxia, 

 Berk., both of which have been found on the roots of Ifevea 

 hasilieHsii'. The former organism is capable of travelling 

 through the soil from root to root, hence it is of prime 

 importance to get rid of all infected material. The soil 

 should also be treated with quick lime, and a circular trench 

 should be dug at some distance from the diseased tree to 

 check the advance of the mycelium. Decaying bush stumps 

 must be destroyed. 



The para.site known as H >j menocheate norta is not 

 regarded in Southern Nigeria as being less serious than the 

 above-mentioned organism. At the same time it is admitted 

 that this fungus cannot spread through the soil like Fomes, 

 and it is therefore dependent for its spread on pre-existing 

 infected material. In this connexion it is well to bear in 

 mind that the rapid root growth of the Para rubber tree soon 

 takes complete possession of the soil in a plantation, and 

 hence if one tree becomes infected, the fungus has a chance 

 of running along what may be metaphorically regarded as 

 a (complex system of railway lines. 



The stem disease of Paia rubber, known as pink disease, 

 caused by Coi-firiu/n salmonicolor, B. and Br., has been 

 identified. It generally attacks at the fork, and in conse- 

 quence, the whole crown very often dies. The fungus is not 

 believed to be a wound parasite. 



DISEASES OF (■ACAO. 



It is stated next that root disease {Ht/menocheate no.ria, 

 Berk.) is fairly common on cacao trees in the Protectorate, 

 whilst one undoubted ca.se of Fomrs scmilostu?, Berk , has 

 been found in the Agege district. The well-known canker 

 disease of the stem of cacao trees is frequently to lie observed. 

 The question as to whether the causative organism is really 

 Fhi/toj'hihora Fal'eri, Maubl., or Sjiintria rolorans, is not 

 entered into. The fact, however, is emphasized, that apart 

 from the uncertainty as regards the specific parasitism of the 

 two species just referred to, there is undoubtedly another 

 fungus at work in Southern Nigeria, which produces effects 

 very similar to the group of symptoms denominated by the 

 term 'canker'. The author regards this latter parasitism as 

 the most serious menace to cacao in the (Jolony. A full 

 description of the disease will be i)ublished in due course. 



As regards pod diseases, 'I'hyridaria tarda, Bancroft 

 (brown rot), and Xectria bainii, Massee., have both been 

 noted; whilst anthracnose, caused by Colletottichv.n ilicj- 

 hroiii'ie, Delacroix, has also been observed. 



DISK ASKS OF fOTTON. 



Possibly the most interesting feature of the report under 

 consideration are the remarks presented in regard to the 



pathology of cotton in West Africa. 'Sore shin' (seedling 

 disease) has been frequently observed; but the disease does 

 not seem to be induced by any specific organism. 



For convenience, the chief diseases attacking cotton are 

 treated under two heads, tho.se atfecting American, and those 

 harmful to the so called native cotton. 



The American diseases are believed to be merely 

 physiological. Bed rust is an example of a disease which is 

 not caused by a parasite. When in this condition, the 

 leaves of the plants turn reddish-purple in colour, and soon 

 fall ofiF. The malady appears to be correlated with climatic 

 conditions. After referring next to the undoubted occurrence 

 of a good deal of natural crossing between the American and 

 the native cotton, the importance of selection of 'proof varie- 

 ties receives attention. It appears that red rust is particularly 

 severe on crosses between the two continental strains. 

 A curious disease, of obscure origin, is referred to under the 

 name of leaf '.sport' of cotton. Amongst other diseases of 

 leaves and fruits observed were areolate mildew, caused by 

 Ramdaria areolia, Atk., cotton anthracnose, induced by 

 Colletotrirhum gossipii, Southw. A species of Diplodia, which 

 is believed to be identical with one on cacao pods has been 

 found occasionally causing decomposition of the boll. 

 Cotton rust is of wide distribution. 



In concluding the report, attention is given to the 

 diseases of native cotton. The chief one is that w-hich is 

 designated 'leaf curl'. It is remarked that the term 'disease' 

 is somewhat misleading, as the particular state referred 

 to is more of an abnormality than a strictly morbid condi- 

 tion. Space does not allow of a detailed account of the 

 symptoms given, but the whole eti'ect may be described as 

 a curious puckering and yellowing of the veins, and lamina 

 in general. No cause can be ascribed to this disease. It is, 

 however, under investigation. 



BEYOND THE MICRO.SCOPE. 



Another pathological condition that has been investi- 

 gated is a blackening of the midrib and main veins of the 

 leaves, accompanied by the formation of a waxy substance 

 which was found to contain bacteria and a Fusariura It is 

 still uncertain which of the two agencies causes the disease. 

 This malady has not been found on any of the American 

 cotton, but it is somewhat remarkable that it has been noted 

 on Brazilian cotton. 'Leaf curl', on the other hand, does 

 not atf'ect the Brazilian type. It is noteworthy that 

 Brazilian cotton bears several botanical characteristics 

 suggesting a relationship with the native variety. It is 

 believed that the modern conception of biological forms of 

 fungi (notably in regard to the parasitism of the rusts and 

 mildews) seems to find illuminating additions in the case of 

 these cotton diseases in Southern Nigeria. 



There is much in biology that lies beyond the microscope. 



A note appears in the Erjieriment Station Record 

 (July 1913) referring to some recent observations carried out 

 by Bateson in the Federated Malay States in regard to the 

 possible occurrence of a bacterial disease of Hevea. 



A specimen was found which did not seem to be infected 

 with any of the common root or stem diseases. The wood of 

 this tree was discoloured to a depth of about 1 inch, the outer 

 portions being dark brown. The manager of the estate from 

 which the tree was obtained, stated that the leaves on the 

 lower branches died suddenly, as though they had been 

 scorched by fire. This cor.dition spread rapidly, and within 

 three days' all the leaves on the tree were dead. The malady 

 is possibly induced by l^cteria. 



