THE AGRICULTURAL NEWS. 



Ff.bruahy 22, 1919. 



PLANT DISEAolS, 



FOOT ROT OR MAL DI GOMMA ON 

 LIMSS. 



The lime tree in these islinds is usuallj' little subject 

 to the foot rot disease, charaoti-rized by the death of the bark 

 cm the i:ollar and the crown roots, to which some species of 

 <;itrus are ver>' susceptible. Cases on limes have howev,-r 

 ">>een reportri from time to time, and at present some 

 >(«ftb1e of this nature is being experienced in parts of 

 ^teeada. 



The disease begin'* in a patch or patches, often m the 

 ■hollows formed by the junction of the roots with the stem. 

 <;um pockets are found in the niij.>bSouihood of the cambium, 

 there is often an exudation of gum through cracks in the baik, 

 the bark dries up or is rotted by fungi and bacieiia, and the 

 ■wood is eventually left bare, and begins to dfc»y. A sour sraell 

 usually accompanies tbe disease. The patch spreads arourid 

 the base of the stem, aud for souie distance along the main 

 Toots, and tbe tree is slowly killed. Qsmlly, as in other 

 ■bark diseases, a thinning and yeilowing of the foliage occurs. 

 and as the encircling of the stem approaches completion, 

 heavier crops of fruit are set. 



Various fungi have been found issociated with this type 

 of disease in ditferent pirts of the world, but, it is generally 

 regarded as of non-parasitic origin. Apart from this question, 

 there is gt^nerd.! agreement as to the cotjdiiions under which 

 the disease is liable to appear. Heavy or compacted soil?, 

 -;„.r,,,f,j2f ^raisagc, r.r.i too deep or too close planting are 

 wecognized as predisposing causes. 



Treatment of existitis cis"s is possible on the following 

 lines: permanently remove satRijient soil to leave the collar and 

 crown roots exposed. Scrape and cut away the dead bark 

 until the patch presents a clean surface surrounded by a 

 margin of healthy bark, and paint the whole place over with 

 Bordeaux paste or a good wood pr'-servative, such as is used 

 for treating pruning cuts Remove any low branches which 

 interfere wi^.h the free circilaiion of air anund the base of 

 the ttpe. At the satne time close attention should be given 

 to drainage and cultivation 



THE MOTTLING DISEASE OH SUGARCANE 



IN PORTO RICO. 



In Circular .Vo. 7^ ofthe Department of Agriculture 

 aud Industry. Porto Rico, two papers are published of 

 creat interest, considering the anxiety caused to the 

 su"ar planters through thi: Weat Indies, by the appear- 

 ance of the mottling disca.se in Porto Rico although 

 the disease has not yet Oeen noted in any other of these 

 islands. A tr,inslation of these papers from the Spanish 

 is given below. The first is by E. D. Colon, Dir- 

 ector of the island L.xpmment Station, reconling 

 fome facts established with regard to this disease. The 

 second paper by F. S. Earlc. Palhr)logi8t of the Federal 

 .liepiirtmeut oi Agriculture, gives practical directions 

 for the eradication of the disease. 



IDKNTITY WITH THK YKfXOW 8TRIPK DISEASK 



The mottling of the cane began to claim the at'entiou of 

 the Porto Rico Experiment Station during the year lOh'iie. 

 It was taken Sot a new and iindescribed di.sease, and as auch 



was smdied up to Kohrnary lOlS, when it became known in 

 the is'anJ that Dr. H- L. Lyon, of [I iwiii, wis of opinion 

 that the disease describtJ by the Piant I'lih >l uisc of Porto 

 Rico, Ml-. J. A. Stevenson, corresponded to one alroidy 

 known and strdied in J.iva and Hawaii under the name 

 of the 'yellow stripe disease.' R^c^i.tly, Dr. Lyon on a visit, 

 to Washington took the opportunity lo examine specimens of 

 mottled cane sent ih^^re from Porto llico, and again coiifirmei! 

 his opinion. The D, rector of the Porto Ricj ^ta•ion his had 

 translated tho mof-t comiiletc de.^cription in e.xistence of thi* 

 disease, published by the S.ig»r Experiment Station of Java. 

 The descriptions which arc given correspond sulEiiienily well 

 with the disease a« known in P irto llico. 



Considering iliis, and set ing that there is no other cause 

 proved, the acceptance of the identity of the 'in >ttltni:d.sease* 

 with the 'y( lliw s.ripe disu.ise' of J iva and II iwaii is jasiilied. 



The idea that the Porto Ric > disease was something new, 

 and that nothing w.asknown of it anywhere else, has constitut- 

 ed a great obstacle in the way of the recep'ion of the fjicts in 

 relitionto it in Porto llico and outside of Porto llico. and 

 is also an obstacle to undertaking with energy and cuiiidence 

 thecampai^rn of endication recoinnii-nded by the E\pcrimeat 

 Station. This obstacle is now swept away. Tbe facts miy 

 now be consideted. 



(1) The ch iracteristic mottling of the disease Oe'imes 

 more diffiiuU to notice i'l prop>rtion as the plant mitures. 



The description from -Java, referred to above says that 'as 

 the plant grows old, the cle.irn^s^ of the phenom-inuu 

 diminishes abng nith its growth.' 



(2) Toe disease reduces the tonnige of cahe, and ii> 

 conseq lence the production of sugar proporti uia'ely. 



In Java one esfporiment gave tin.' lo') nvin^ results; 

 healthy cane, fir.st crop, 2r2,'$ tons per acrr; diseased cane 

 first crop, 18-2i) tons per acre Iij HiWaii auoiher expiri. 

 ment gave the following res ilts: healthy cine, calcnia'ed ton- 

 nage per acre, 10113 tons, iiving a yield of 1-1-9S toa.s of 

 sugar; diseased cane, calculate! tottnage per acre 56 21, 

 yield of sugar 8 '43 tons. 



\3y Neither manure nor water, nor intensive cultivt^ 

 tion cures the disease. 



The experience of the planters of the north and north- 

 west coast of the island, that of the experiment st iti ons of 

 Central Fajardo, and of .I.iva leave no room for d lubt oa 

 this point. 



(4) Disinfection of the cuttings with Bordeaux mixture^ 

 lime, formalin, or corrosive sublimate has no marked etTtcfc 

 on diseased cuttings. 



In the experiraonta at Central F.ijardo, 100 per cent, of 

 diseased cuttings gave 100 per cent, of di.seased shoots after 

 treatment. 



(5) Some varieties of cane offer more resistance to tb^ 

 disease than others 



Accoiding to Dr. H. L Lyon, in Hiwaii the Striped, 

 New Guinea 15, and I). 1135 are very resistant. D. 43J 

 has proved resistant in F.iJAido; in experiments carried oufc 

 by the Departmenr of Aijronoray of the I'jrto Rico Station, 

 B.1596, B. 3412, and Yellow Caledonia have proved re.sistant, 



(6) Th' diseiiae is transmissible by vegetative rcpro* 

 duction; almost wichout exception diseased cutiing.s produced 

 diseased canes. 



Of the total of 628 canes growing from diseased cutting* 

 in the experiment in Hawaii mentioned above, only three 

 canes could he reckoned as apparently healthy In Javi an 

 experiment was carried out with iho following result. Sir 

 lots were planted completely with diseased cuttings ot the 

 variety QZ. 1 39. The percentage of diseased shoots on an 



