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THE AGRICULTURAL NEWS. 



August 2, 1913. 



FUNGUS NOTES. 



THE SPOTTING OF PLANTATION 



PARA RUBBER. 



In continuation ot an article on the causes of this 

 iuftctious condition of ruMier, published in the last issue but 

 -one ot the A<jrindtural Nefs, an account is now presented 

 •«jf the methods of treatment, as described in Bulletin No. 16 

 of the Department of Agriculture, F.M.S. At the outset it is 

 emphasized that it is essential that the cause of the discolor- 

 ation should be ascertained before any preventive treatment 

 can be applied. 



.-^TEMyiEl' CIJEPE SUSCEPTIBLK. 



(Jiie imi)ortant condition under which spotting occurs is 

 in damp low lying situations where the facilities for drying 

 are not adequate; where good access and good circulation of 

 air are not obtained, spotting may be frequent Reviewing 

 aome of the forms of prepared rubber which develop spotting, 

 it is stated that thin crtpe appears to be less susceptible 

 than thick crOpe; while artificially dried crOpe, as far as has 

 been observed, has not been found to become spotted. 

 Steamed crOpe which takes a comparatively long time to 

 dry, appears to be very susceptible to spotting. 



VALUE OK EAI'Ill BRVINti. 



Owing to the fact that no organism can grow if there 

 is not suflicient wattT present, it would appear that rapid 

 drying should diminish the quantit}- of spotted rubber. In 

 this connexion it is interesting to note that rapid artificial 

 drying, which is completed in a few days, altogether prevents 

 the development of spotting. It would seem that the 

 adoption generally of artificial drying on a larger scale has 

 been prevented by the fluctuation in the form of rubber 

 ■which meets with favour on the market. 



SMOKEI' KUUBEl; IMMUNE. 



Spotting due to fungi and bacteria has not been found 

 on smoked rubber. Id most cases this would appear to be 

 due to the presence of creasote and phenol compounds in 

 the fuel employed. 



USE OK KOUMALIN IN THE IIELb. 



In dealing with the possibility of applying chemicals, 

 it is pointed out that t' ; objection to the use of metallic 

 salts is the fact that, the presence of even small quantities of 

 <)f such substances in plantation rubber might bring the 

 product into disfavour on the market. As regards fluid 

 antiseptics, larbolic acid cannot be employed owing to its 

 dark colour. For preventing spotting due to field infection, 

 the use of I part of foruialiu in 400 of latex is advocated 

 as likely to prove efficacious. The cost of formalin in 

 London is about 55 ■. per cwt. 



.SULI'HUR EUMES. 



The means of sterilization of the drying houses next 

 receive attention, and the most suitable for the purpose 

 is stated to be the employment of sulphur fumes. It 

 is important in this connexion to render the buildings as 

 air-tight as possible. It would probably be necessary to 

 repeat the di.siufection at intervals. 



IMPORTANCE OK I.^OLATIoN. 



Lastly, emphasis is laid on the matter of isolation of 

 spotted rubber. When spotting is caused by Hacilhts ju-ndi- 

 i/iofiis, the rubber should be isolated as early as possible. 



Sheet or crepe which is spotted by the bacillus should not be 

 packed among other rubber for shipment. In conclusion, it 

 is stated that there is an accumulation of evidence, which 

 indicates that clean rubber packed under most careful .super- 

 vision was found to be spotted on arrival in London. This 

 point will presumably be further investigated. 



A NEW DISEASE OP THE CASTOR 



OIL PLANT. 



A continuation of this subject, an account of which was 

 commenced in the last issue of the Agricultyrnl Xexvs, is the 

 following description of interesting facts of practical signi- 

 ficance connected with the behaviour of the fungus 

 (Phijtophthora /larasitica) in pure culture and in inoculatioa 

 tests. 



DIFFICULTIE.s IN 0BT.4INING A PURE GROWTH. 



It is generally a troublesome matter to obtain a pure 

 growth of fungus in the case of leaf diseases. In the present 

 investigations, direct inoculation from diseased leaf to culture 

 medium was always accompanied by the introduction oi 

 fungus saprophytes and bacteria. A successful procedure, 

 however, was to cause a piece of diseased tissue to discharge 

 zoospores (swarm spores) in sterilized water. A sterile piece 

 of healthy leaf was then inoculated with these spores, 

 followed by a transfer of the new growth on to nutrient 

 pith. Finally, a portion of the new mycelium was intro- 

 duced into a tube of French bean (Pliaseohis vulgaris) 

 juice agar, which gave in two days, a pure, rich, healthy 

 culture. 



BEHAVIOUR OF FUNGUS IN CULTURE. 



Amongst other things it was observed that sporangia 

 (fruit bodies) from cultures, made when the temperature was 

 very high, did not discharge their swarm-spores as readily 

 as when the temperature was low. Light, also, seemed to 

 influence the formation and emissiion of zoospores. It 

 hastened their discharge. 



KE.STING SI'OUKS. 



In culture.s, and on inoculated castor fruits, a second 

 spore form was found,— the resting conidium or so-called 

 chlamydospore, which also occurs in the case of the Cacao 

 Phytophthora, Extremes of temperature do not retard 

 the formation of these spores as occurs in the case 

 of zoospores. When sown in water, restingspore.« 

 germinate readily in twenty-four hours. The germ- 

 tubes either directly produce si)orangia, or resting conidia 

 or vegetative hyphae. If kept moist, chkmydospores 

 retain their vitality for over nine months, but if they are 

 completely dried, their, germinating power does not last for 

 even a week. This fact again emphasizes the close relation 

 between climatic conditions and the reproduction of this 

 parasite. 



SEXUAL IlEPHoniCTIOX, 



The fungi belonging to the group represented by the 

 organism in question is not content to propagate itself bv 

 budding, or vegetative means alone. It has a sexual stage, 

 and in the case of Plu/toplithora fnrasilH-a, the' oogonium 

 (or female element) arises from within the antheridium 

 (or male element) This fact is of importance for purposes 

 of classification. It distinguishes this fungus from all other 

 species of the genus except Fh. Colocasin-. 



INOCULATION l..\PEl;I.MENTS. 



The results of inoculation experiments are always of 

 interest to the general reader because they determine te 

 what extent the fungus is able to do harm. 



