2-5 t 



T1IK AGRICULTURAL NEWS. 



July 31, 1915. 



FUNGUS NOTES. 



A NEW FORM OF BLACK ROOT DISEASE 



ON CACAO 



i - taken from a report made by 



Mr. Win. Nowell, Mycologist to the Imperial Departmet 

 Agriculture, on fui Lcao in Grenada. After 



a discussion of the familial' type of black root disease, 

 • 1 in wet districts in Grenada, as in St. Lucia and 

 I tominic i chi reporl cont inues under I tie heading The 

 Lowland Form, as follows: 



The cases oi i i lisease seen during this visit on 



thr lowland estates pi I some constant features oi 



difference in their syiupt from the disease already 



This might have been put down to the effects of drier 

 conditions had not the finding in connexion with the disease 

 on two widely separated estate bi the perithecia of a distinct 

 species of Rosellinia led to the conclusion that we shall have 

 to recognize the existence of a separate, though close allied, 

 disease. 



On one of the estates earliest visited I was shown 

 a group of dead and dying fives, which though ascribed by 

 our conductor to beetle injury, had the general appearance of 

 the effects of root disease. I had the collars and surface 

 roots of several trees cleared but found no sign of llosellinia 

 mycelium. The regular occurrence of new suckers on the 

 failing trees also presented a feature which 1 had been 

 accustomed to regard as absent from cases of root disease. 

 Time did not permit of tin- clearing of the lower roots. On 



the next estate an area to which attention was called as 



an example of the effects of thrips presented the same 

 symptoms: trees slowly failing, putting out suckers low 

 down on the trunk, and ultimately dying. 



Again no symptoms were visible on the collar or the 

 upper root- but the general appearance of the group of tree- 

 was so typical of a root disease area that I arranged for 

 a tree to be dug out. On the lower roots of this was 

 present a white mycelium closely resembling that of the 

 upland Rosellinia, but more scantily developed. The trouble 



in this instance appeared to have had its origin in infec 

 tion from stumps of teiidre acailloua (Piptodt nia peregrina) 

 two tree- of which had beei i at down a few years before. 

 The same type of disease was afterwards met with on 

 ral i the mpt >nis wi re as described above, and 



the presence of the chat mycelium was verified in 



most cases. The disease works in essentially the same way 

 as ti' upland form already described, and ultimatelj 

 produce dead and dying trei 



It appears however to lie sl< iwer in its action, and the failure 



it the trees is much more lingering. With one exception, 

 -which may very well have been at isolated case ol the up] 



myi < 1 1 it Li oi that disea 



was not i ' ai on the lowland estates. <tn two dead ca 



stump-, one in the midsl of a ol dead and .lying ti 



tl thei whi i, tree ha out, the perithi 



tdy mentioned were found, as with white 



mycelium such as was found on the dyn 



The conidial fructifications found with th perithecia were 



old, but could In- made out to hi- me typ 



in other 1 1 i Rosellinia. The i I form a layer 



on the surface oi tl looking like very fine shot dusted 



thickly upon it. 



TBI \ L'MEN I . 



Tin- treatment of this disease should follow upon exactly 

 the same lines as that of the upland form: isolation oi infected 

 i complete dest ruction of infested 1 1 



Diagnosis is much more difficult, and the planter may have t< 



proceed largely upon suspic Winn one or two dead or 



dying tn I i been dugout from a -it nation and the 

 of the fungus verified, other cases occurring in 



similar circum with re certainty. 



The slower rate ot attai more chance of stopping the 



spread of the disease It may even be more feasible to cure 

 infected trees than is the case with the upland disease, and 



■ planter claimed to have effected cures with lime or 



copperas. No tree which has not been isolated should howevei 

 be allowed to remain in the hop.- of a cure, and no treatm i I 

 should !»' attempted of trees which are far gone. The 

 ill eased roots which can be got at should be removed, lime 

 forked into the soil, and the leal hi il the tree should 1m 

 reduced to make up for the loss or failure of roots. 



FIXATION OF ATMOSPHERIC NITROGEN 

 ON A COMMERCIAL SCALE. 



Besides constituting an important landmark in the devel 

 opment of agricultural science, the fixation of atmospheric 

 nitrogen artificially is a notable matter at the present time, 

 on account of the fact thai those countries which an- subjected 

 to a blockade in the present war have hugely to depend 

 upon this method for obtaining substitutes for nitrate of 

 soda. The Louisiana Planter for May 29 contains an 

 instructive article on the subject from the pen of 

 Dr. H. C. Prinsen Geerligs, and in this the different methods 

 utilized are described. 



The idea of utilizing atmospheric nitrogen originat- 

 ed with the British chemist, Sir William Cn 

 and for many years now nitric acid has been made 

 from nitrogen and oxygen of the atmosphere by forcing 

 air through a chamber in which a very powerful electric 

 lamp burns in a magnetic field. It will be unnec- 

 essary to describe in this article the various reactions 

 which take place subsequent to the production of calcium 

 nitrate, a salt which has already obtained considerable 



popularity as an artificial fertilizer. 



A second method of fixation of atmospheric nitrogen is 

 the heating of calcium carbide in a current of pure niti 

 gas. This method gives rise to the well known calcium 

 cyanamide, which so far ha- not proved very satisfactory as 

 a manure. 



A third and particularly interesting met hod consists in 



conducting a current of niti i aluminium carbide, 



which has previously been prepared in an electric n 



from aluminiun le an,d carbon The react i< m w hich 



follow-, turn liuminiuiu into aluminium nitride, while 



rent of carbot m xide escapes, which n ed as 



fuel, The aluminium nitride in its turn is transformed into 

 aluminium oxide and ammonia, of which the former may be 

 used as a ran material for the manufacture of mi 

 aluminium, while the latter is the nitrogenous material 

 ed. 



