T?0 



THE AGRICULTUKAL NEWS. 



JjiJfUAEY 25, 191&. 



PLANT DISEASES. 



PLi^NT DISEASES IN JAMAICA 



The repcrt of the Miorn V -...log'st, Mr. > F. Asliby, in 

 *lie AnnuHi Report on the I'epi-rtmcnt of Agriculture, 

 Jninaica, for tbe j'ear emlea .March 31, 191JS, contains 

 much of interest to West Indian readers. It is largely 

 teptfiduced below. 



It appear.* that the nuiubfr of samples collected or 

 forwarded to him for e.xamiri,-i!icn during the year reported 

 en was lOb, apportioned ;unoDg cultivated crops in the 

 foUowirg way: iianana?, I'l: coconuts, ;">!: miscellaneous 

 (mainly canes, citrus, and cacao), 36. 



i;\N\N'Ai-, 



I'oiiiiiiui Visaist or /ui/itinn //'///. — Cases ha%'e been 

 found in districts hitherto free from diseise, and new centres 

 ci! cultivatiors diseased in the previous year. In the district 

 where disease has been found constantly for the last six years 

 the cultivators have begun tn give main attention to canes 

 and j-round provisions, so that fewer cases may be anticipated 

 in the coming year, ."^oils in bananas from several parishes 

 have been examined (dilution.s planted out in acid sugar 

 aeparagan agar), and in all cases have yielded fu.saria. Two 

 species were found in abundance — fifty 4.000 colonies from 

 the giram "f .soil — one very like the kind causing disease 

 ^a variety ol I'lisariiim ••usi/i/'t'iliiiii, .Xtk.), and the other 

 J-. riiduid'Ui, Woll. The former kind (at least two varieties) 

 was frequently as abundant in banana soiU where disease 

 was unknown as in soils around afi'ected [jjants; a form 

 absolutely identical in growth, reproduction, odour, etc., 

 with the kind always isolated from the diseased plants, has 

 not been separated from soils. (Jases of other banana diseases 

 have not teen reported during the year 



CdCo-M'Ts. 



Hud rut. — This disease {or diseases) is causing appreciable 

 I0.-8 on a number of estates in the eastern parishes 



The shaking and breaking of limb.-i by the hurricanes 

 jn three suc.(5e.-isive years, with the consequent sei-b;ick in 

 growth have weakened the trees, and made them ready 

 Victims to attack by parasites Many cases of bud rot have 

 .shown up within the la.st two months in trees not badly 

 damaged by the September hurricane. The disea,>e in the 

 eastern parishes thows as its tir.^t visib'e symptom, a wilting 

 and withering of the heart leaves. A soft stinking rot i.* 

 usually found in the heart (stulk.s of youngest leaves, anti 

 tbe apex of btem)- 



The base.s of the young limb.s around the heart show 

 spots penetrating the strainer, and even going through the 

 thicker part.-. In sucli spots, and in the heart where the 

 tiwne i.i not soft rotted, mycelium of the Phytoj^hthora type 

 i.i present. A I'hytophthora like fungu> has been isolated 

 from heart-leaf sprjts in a casi ol' bud rot, from water soaked 

 til-sue "f the limb of thi- heart le.if, and from the husks of full 

 grown V>ui iminalure nutn. This fungus, obtained in pure 

 culture, is very proViably identirnl with l'\lliiiiiii />ii/i>iiriiriiiH, 

 |{utl , whii-.h has many characters of a I'hytophthora. P.f<a/in- 

 r'ortitn cau.nes bud nit of coco-nuts in India. Its probable pre- 

 Hence in the West Indies rai.-e.- the fjuf.^tion a.s, to whether 

 Hiuii'rnim loii (or its allies) is ever tbe primary cau.«e of 

 a bud rot, and whether it can reach to and enter the uninjured 

 heart tissues without the aid of the fangu?. 



Another peronospore fung\i9, an undoubted species of 

 I'hvtophthora. has also been isr.l',ted froni coco-nut limbs on, 



several otcasion.s; it was ff.und in extensive spot;sand patche.-" 

 on the bases of older limKs in the thick tissues ai.d the 

 strainer: in the trees examined it was working in from limb 

 to limb, but too slowly to reach the heart. The preventive 

 treatment referred to in the report for 191(i 17 was continued 

 on some estates in St. Thomas, hut was ended abruptly by 

 the hurricane. . The results were uneven and, on the whole, 

 unconvincing. A series of well planned e.vperiments covering 

 two or more year.-, financed by Government (Imperial), and 

 under the control of a mycologist, is necessary to work out 

 the problem of preventive treatment. Kesults would be of 

 the greatest vtilue to coco-nut planters in all British tropical 

 countries, as bud rot is now very widely spread. 



Leaf Bitlfii Disci,Si.s {I.taf /,V/, ). — These diseases have 

 been treated on an extensive scale by planters in the north- 

 eastern parishes. Promising results have been obtained iu 

 spite of the hurricanes 



.Misri:i.i.ANKi>r-. 



The gall disease of sweet potatoes, di:e apparently to a. 

 species of Albugo, showed further e.xtehsion in upper Trelawny. 

 The disease of pimento with 'fire blight symptoms w.-ts 

 again observed on one property. The cau.sal fungus wa.s 

 again isolated, and yielded a perfect; fruiting stage, proving it 

 to be /iVf//(7/(f <v///c«£', Zimm . Collee in the |fime field was 

 not affected. Corticiiim ?v/!;7/«, var. sulaiii was found to be 

 tbe cause of a rot of yam.s. working inwards and causing a 

 separation in layers. 



Samples of potatoes (Irish; from several points were 

 attacked by late blight {I'liylnplilhara iiilcf/a)ii\ in .January 

 and KebrUHry: the di.sease migbt be brought in the imported 

 tubers u.sed for seed<, and its appearance here connected with 

 its severity in the e.vporting districts of Eastern Canada, 

 during the preceding summer, (iiowers of pot,atoe.s in the 

 upl;iiids should make a point of sprayinij with liordniux or 

 F.urgjndy i:iixU:re six weeks after planting, and repeatiiij;^ 

 once or twice more, in dependence on weather. 



A defect of coprs, known as h'>ney comb, was 

 found to be caused by Jiruii'/ns MCwuUria/s v///x'(i/i/s. 

 The strain was markedly thermophi'e, as it grew on meat 

 and caused the fault at » temperature of ISO F. Copras from. 

 hf't air and steam pipe driers are atfected. Fumes of burning 

 .-ulphur entirely prevent the fault, the critical period being the 

 first ten to twelve hours in the drier. 



The fungi parasitic on the spiny citrus Hy (. //c/.';wr//?- 

 /////.< l}'i'i;/iii/ii), which have become conspicuous in .some dis- 

 tricts during the last few years, continue to exercise an appre- 

 ciable control of the lly. 



I)uring the latt; r part of the year, thanks no doubt to 

 a period of over cast sky and rather freijuent showers, they 

 were well developed in cultivations on the south side dry 

 CO istal plains. Three such fungi are active here: — • 



I. Tbe I'.riglit Ued fungus '.{.Isr/iersonia a/i'yrodis). 



■J. 'I'he Dull lied fungus (. I.\i:,ri/a lV,'/>h,tri)'. 



-"•. The Cinnamon fungus ( /Va//;-//////;// hi'lerodiitiuin). 



The first and last produce micro.scopic spores in abuud- 

 ance. hence can be spread easily by spraying on the trees 

 a auspen.iion of tha spores in water. The second produces no 

 true spores but ■\ restricted number of brown rather largf 

 blackberry-like bridies bearing blunt spines, and are scattered 

 on the silky strand- of outgrowth on the under sides and 

 edges of the leaves: the spines germinate quickly, giving rise 

 to long infection threads; this tungus has all the vegetative 

 characters of a Oortiiium, and its reprmluntive bodies may be- 

 rudimentarv sclef.'ti.' 



