54 



THE AGRICULTURAL NEWS. 



Maech -23. 191 S. 



PLANT DISEASES. 



PROTECTING CITRUS FRUITS AGAINST 

 ROTS IN TRANSIT 



6outh of Porto K\co little interest is trvkeii in the ship- 

 ping of oranges and grape fruit, save fc.i unimportant and 

 unorganized inter-island trade. The only citrus fruit industry 

 of importance is the green lime trade with New \ork. In 

 this case, when the fruit i- well selected and packed accord- 

 ing to approved methods, the losses from storage rots are 

 not, so far as the writer is aware, of serious consequence. 

 "The complaints which have been made would seem to have 

 reference to poor quality and careless packing in the ship- 

 ments made by speculators during periods of heavy demand. 



In l*orto i'lico and the Isle of Pines there is a develop- 

 ing trade in grape fruit and considerable attention has to be 

 given to prevention of losses in transit. A recent paper by 

 J. M. r.odger.s and F. S. Karle {rhytif,iUuihi:^\, YII, 361), 

 who are working at San Pedro, Isle of Pines, records the 

 discovery of a simple and effective method of protecting 

 citrus fruits against stem-end rot. It may find an applica- 

 tion in the P>ritish West Indies in the occasional shipments 

 made to England, and may even come to have nn interest 

 for the green lime trade when the growing competition leads 

 to more discrimination as to quality. 



Mf)st growers arc by now acquainted, at least, in theory, 

 with the dictum that fruits for shipment should be handled 

 as delicatel.v as if they were eggs, but it -was found at San 

 Pedro that even this did not suffice. I'ruit picked under 

 direct supervision of careful foremen, by labourers wearing 

 cotton gloves, placed in standard field crates, and hauled to 

 the packing house on waggons with bolster springs, graded 

 \>\ experts, and every doubtful fruit rejected -conditions which 

 ■would suggest the millennium to any planter rif the writer's 

 itcquaintance — still showed a large amount of decay in 

 transit. 



A large proportion of the loss was found to be due to 

 Diplodia rot starting from tbf stem end of fruits with no 

 apparent injury. A Uiplodia spccie.s, it tn.iy be remarked, 

 appears to be common on ripe limes throughout these islands. 

 It was noted that fruit which had been clipped, retaining 

 the i;aly.x, showed much moie .susceptibility tlian fruit which 

 Lad been pulled, owing to prevention in the former case of 

 ijuick drying out of the stem cavity. 



'I'he fir.st attempt at protecting the frnil was made with 

 paraffin wax. The coaling of the rind with this -ubstance 

 did not materially alter the amount of loss from rot, but it 

 prevented the fruit from shrivelling, and made it possible 

 lo keep tliii»-»kinned lemons in excellent condition ffir two 

 or three mouths. The application of p.araftin to the stem 

 ends gave promising results as a measure against stem-end 

 rot, but was not altogether satisfactory because the material 

 did not stick well. 



The next method tried was so successful that there was 

 no necessity lo seek further. It consisted in the apfMicfttion, 

 to the stein enfl of pulled fruits, of shellan dil'ited ti-> n thin 

 consistency with alcohol It is easily and c|i'ickly applied, 

 aticks well, an<l seals the cavity jK-rfecl 1_\ . Witii clij'ncil 

 fruits the reau'ts are much less eati-f«ctnry. 



The difffience between pulled and clipped fruit was 

 consistently high all through the experiments, and is in itself 

 at least as signiticaiit as the differences obtained by coating 

 the stem end. Incidentally it was found that washing, in 

 running water or in a tank, .so increased the amount of 

 decay that in the authors' words, 'the use of a soaking tank 

 is the greatest possible folly.' 



The conclusions reached may be thus .set out: — 



(1) That citrus fruit should be pulled, not clipped. 



(2) That coating the stem cavity with shellac largely 



prevents stem-end rot. 

 (.3) That Coating the rind with paraffin keeps the fruit 



in good condition for an additional month or six 



weeks. 

 (4) That washing the fruit induces heavy losses. 



W.N. 



USE OP OFFAL MANURE AND DRIED 

 ■ BLOOD. 



Offal manure from abattoirs, as is well known, is the 

 residue that has been steamed in the digesters to remove 

 grease, and then steam-dried (with constant stirring) in 

 jacketed iron cylinders until it is dry, and is reduced to 

 a fine mechanical condition. It can be dried economically 

 ,so that it does not contain more than 10 to 12 percent 

 of water, and in this state may contain as high as 5 to 7 

 per cent, nitrogen, and 1.3 to IG per cent phosphoric acid. 



Blood from the abattoirs, which is dried in the same 

 way, is generally considerably higher in nitrogen, but it 

 contains very little or no phosphoric acid. The average 

 composition of good samples of these products is given in 

 the Ai^fitiiltiiral Gazette of .Aifc Soiit/i JJ'ii/es for I iccera- 

 ber 1917, as follows: — 



Offal, Dried blood, 



per cent. per cent. 



Nitrogen COS lO'Tl 



Phosphoric acid 12 '87 — 



I'rfim the analysis it will be seen that dried blood is 

 a purely nitrogenous' manure, whereas offal manure, though 

 poorer in nitrogen, contains al.so phosphoric acid. Neither of 

 them, therefore, is what is known as a complete manure; that 

 is, they do not contain those elements required for plant food^ 

 namely nitrogen, ]>ho3phoric acid, and potah, in which soils are 

 often deficient. In the case of offal manure [)otash salts or 

 ashes containing potash, must be added to make it a complete 

 manure. In the i ase of the dried blood manure, both phos. 

 phate and potash must be added to make it complete. 

 ])ried blood comniauds the higher price per ton on account 

 of its higher content of nitrogen, which is the most expen- 

 sive of the manorial ingredients. 



The following method and rate of application of these 

 manures are given in the journal above quotcd:-- 



METiioD oi .MPT.icATioN. — Both offal and dried blood 

 are best brf)adc;istcd and lightly harrowed in. This 

 should be done before the .seeds are sown so that the manure 

 may be well mixed with the earth, and not come in contact 

 with the seed in its raw state. Kor I'ruit trees or standing 

 crops it can be applied at any time as a top dressing, being 

 mixed with loam before application, or lightly harrowed 

 in immediately after. Thorough mixing with the soil is 

 es.sential, as the etliciency of the manure depends upon 

 its fermentation. I'or this reason moisture is necessary. 



