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This Kwn it fflimd at tlw radudion ratio etwekad batow / C« doctHDMit Mt fflmA au laux da rMucthm imMqu* ei signifie "A SUiVRE", le symboia ▼ signifie "FIN". Mapa, plataa. charts, etc., may be filmed at different reduction ratioa. Thoae too large to be entirely included in one exposure sra filmed beginning in the upper left hand comer, left to right and top to bottom, aa many framae aa required. The following diagrama illuatrata tha method: Laa cartaa, planchaa. tableaux, etc., peuvent Atre filmte A dee taux de rMuedon diffirents. Lorsqua la document eat trap grand pour itre reproduit en un saul cliche, 11 est filmA i partir da Tangle sup4rieur gauche, de gauche k droite, et da haut an baa, an pranant le nombre d'imagea n^caaaaira. Laa diagrammas suivants iliustrant la mithoda. 1 2 3 1 2 3 4 5 6 'Mooam nsowTioN tbt chart (ANSI and I'.O TEST CHART No. 2) APPLIED IM/C^P U- '653 tau Mom Slr« ('16) 2M-5MS-FO. DOMINION OF CANADA. DKI'AKTMENT OF AGRIcrLTritE. EXPERIMENTAL FARMS. J. H. QRISDALE, B. Agr., Director. H. T. aussow, Dominion Botanht. DIVISION OF BOTANY THE CONTROL OF POTATO DISEASES H. T. GUSSOW, /dominion BoltmiU* CIRCULAR No. 9. Publi»h«d by ■uthority of Hon. MARTIN BURRELL, M<»»i»tor of Airieulturo, Ottawa, Onl OTTAWA GOVERNMENT PRINTINQ BUREAU 1915 76108 THE CONTROL OF POTATO DISKASKS. RV IT. T. rriissiiw. Ihiiiiininn I'lrfiinixl. It is a flifficiilt matter to arive an actual estimute of the annual losses for the Diiiiiiiiiipti. due to plant diseases atTocting the potato crop. Judgini; from u oonsider- ablc iiiimhrr of ohbos, the total loss must be enormous in some years particularly. The loss from the so-calli'd " storage rots " amounted in some oases to 40 per cent Thi' yield, owiiipr to the use of diseased seed, as far as eiin be judired from "mi»se«" in tile Holds, has been occasionally reduced l>y some '.W |x>r cent, and diseases affectinc the (trowins: plant may also cause considerable damage to thi' I'rop, In nrdiT to prevent such loss and make the cultivation of potatoes more profitable, it is nei e^'sary to strictly follow certain lines laid down for the elimination of discasM, when it is reasonable to expect that the diseases will be eventually exterminated or reducetl to a minimum. Any objections a farmer may have to carrying out the follow- ing siisRcstions will disappear when he finds from experience that their observano* results in a greatly increased yield and higher profits to himself. A. The IKseaset of the Seed Taber.* 1. The presience of the following diseases or insect pests, scheduled under th« "Destructive Insect and Pest Act" of the Dominion of Canada shall disqualify any lot of potatoes for seed purposes, viz.: Potato Canker, Powdery Scab and Potato Tuber Moth.** Potato Canker is not known at present in Canada. Powdery Scab occurs in the Maritime Provinces; no cases of this disease have been observed west of the province of Quebec. In order to prevent the dissemination of this disease, all potatoes grown in the "infested area" are being officially inspected and certified before shipmei'* All bags or other con .i' s "'ed "First Grade Potatoes" will contain inspected potatoes that were grown . *d area, from seed not infected by powdery seal) and on land tliat has nc f produced an infected crop. Only potatoes so cer- tified may be safely use • ''< The Potato Tuber K. ^i known to occur in Canada. Information concern- inpr same may be secured by writintj to the Dominion Entomologist, Department of Asric'.ilture, Ottawa. ■2. Potatoes entirely free from all diseases or blemishes are the ideal potatoes for seed purposes. ^. When selecting potatoes for planting, all bruised, decn.vod, externally di=onsed or unsound tubers should be removed. • Attention la hpri" rtlrfftcil tn FiTners' rlrcular No. 4 pntitle'•>• Nott) 1.) ti. When dr.v, luttinir the potut'iex for •'w-is" will (•omiiieiiep. Provide lach perMin •iViiKih! with a pc)tll^l kiiile, and keep a iiiiniU'r of knirei* in a w.ioden pail i-ontiiiniiiK • loliition of 1; KKKi bichloride of nuTinrv 7. The rtleni end of the tuU'r is the seat of gpvcral in'emul diiK'-scri. Cut a thin •lice off the stem end of eaoJi potato; if perfectly •ound aiior orop wilii the exception of potatoes. ({^Pf Note tM. C. The Diseases of the Growing Plant. Tlio recognition of diseases notiiviible only in the growing plant will invariatjly oe most diffi ult. Where doutt exists, a speoimeii Khowing tlu susi)octe(l trouble should be mailed to the Dominion Botanist for his advice, but. gniiorally .speaking, cureful attention to the elimination of disease in the seed tubers will have largely reduced the disease affe<'tinp the growing plant. Farmers should make it a rule to iiiinieiliiit.'ly remove any individual hill that may show siftns of yellowing, curlin+r-\ip of Icavtv or otherwise fe<>ble irrowth. as weU as any individual plant witli flowers of a ".ill'cK'ut colour from lie icst, in order to keep vnrietics pure. D. Spraying (>(« Note 5). 1. Sprayinji is practised for two main reasons: First, to eontr.il the r,,lor;ido Beetle; and. second, to control Late Blight. Tliere arc otlicr ininnr rcisnu-. 2. KxiwTiments have shown thiit several solutions will stroy the Color. iib, IJci tie, but the solution acting most rapidly is the one to u.se. 3. Spraying must be done thoroughly. All plants, and all parts thereof, niusi i|ie well covered. A plant with one half !riir,iv,>J and the other half misso nf wiitiT, ti. l).i not »pra.v on very wimlv days. Spniv larl.v in llip niMrniiur. or loninKiu'e two hourg Wore »uns\\ eiiiitajninii oni- pound o( blupstone in every fiftepii uallons of wash. 4. Storage [ihu'es shuuM 1m' dry. well ventilated and eoul. The tetnpeniture nhoiild be uniform and not belnw :i:> ' F. nnil not above n»' F. Store p.itatopK in hulk, not in barrels orbajrs. Providintf the tubers wi re mature when harv,-ted. the loss in stmau'e amoiintinff fonietina- ti. niorp than on<-lliird of the crop, will bt jsnutly, if not entirely reduced, if the aluve condition- ar( 'ullillerl. NOTES. 1. Using Bichlonde of Mercnry. Riehlorlde of luereuiy is a deadly poison. Wliili triMtinc or drying treafi'd potato, 'ind \ lien disposint; of used solutinn. kjep all t'artn anii:;iiU uMay, 1 p. 1 of bichloride will make Ji'O Iinperinl nalbriis nf solution. The cruile bi- chloride oif mercury ilisylutiiin are often n-com- mi'Tob'd. but bichloride of men'ury has niven the best results all round. 2. Stable Manure and Artificial Fertilizers in ■ lation to Common Scab. From the disease point of view, sta'ble manure diould not be used f,.r putatoes. This is likely to result in a scabb.v crop, whii'h is larjjily averte ' by the use of frrii- lizers. When there is a hiik of bunius in the soil, an a|ipiicati(i|i ,f crumliled peat will be found useful. Thi- will also retain the nioi-ture in li.irht -i.ila. H. DiKi inl at oinM' Jl tuliiT!* Mmwinif iliwiiluiiriitiun. wlwii rut uh iiIkivc, ut tin- •t«ni end. aijil thrnw imi I*' 'se sliowiiiff «n.v kiml of tpottiii(r in»iJi', thoiiirli the «tfm tod itM.'tf may linvc HhdW.i ,,ii diiMMiiM). 0. Iluviiitc UK<'(I till' k.iife on a luli«'r dliowinir any kiinl of diiii'i)loiiriiti that tuut >nit tlinmBli a diM'uwd lulxr > n-.v.s c. rtuin diMUM-H ti) the iifw tul«!r. Uiiuv ii ;« very iiiipMrtiint tci cluini.'.' Un> kiiilf iiltcr huvinK thrown out u dimuinoil iuImt. It in wniiti- of tiiiip (n fiit ■,\,\ hntvtu iputK and iit lh«> reat of tho IuIht. After fiillii»iTi(f tliiM' prfciiutioii!', evcrythinir ha* bii«<'!i •onviyi'd l)y unsfiund »«<) putatMos. 'I'lm wtn an- now nvnly ''ir pliintiiijf. B. Diicue-infected Land. In the PBSo of I'uwd( ry Scali uiid u uuiiili'r of otlitT potato di^ra-cs, the I'uiisal anisni porsint* in tlie soil for a uunibcr of years; it in. therofore, ne<'C!*!.ary to avoid too freinent mircossion of |Hitato crops. Onliiiurily potnturi* nhoiihl not he (Unwn oftener on the same land than e\-ery fourth year. Where I'owdory Sc-ah has exi-ti'd, it i* adviwihle to chaniro to latnl that has not pre\ioti«ly proly remove any individual hill that may show sigrns of yellowing, eurliinf-up of leaves or otherwi.se «>Me growth, as wdl as any individual plant with tloucrs of a dilVin ut colour from tie rest, ii^ order to kC'ep varieties pure. D. Spraying (^ Note 5). 1. Spraving is practised for two main reasons: 1 irst, Beotli ; and, second, to control I.ale Blight. There an mi 2. Experiments have shown that several solutions will oe-troy bnt the solution acting most i.ipidly is the one to \i.se. .'!. Spraying must be done thoroughly. All plants, and all pi well covered. A plant with one half sqirayed and the other half un»pra)"»>d part eaten off by he he«'t!es very quickly. Thi, will to continue the ptast. One spray thorouglily applitnl is b. .ter th applied. 'ontr .1 nnr re the (V irts tl;< missed leave i the C ■S'lU-, Te.it will h Iiougl rul ea oloraclu II.. tie. UUsl lilO ave the beetles rehssly i. \\e rMMiriuiirii.l t».. »\<,',iu\ ni'l'li.iiii.n, f..r I...1I.- ; ,.iir wlun tho ploiit. Hr« (roth iMiir b. mx ii,<'lii'» liiuli. t<> U- f..|luw.-,l l,y iirii will niiliinill.v vhp.v u nliiia 1.. ihv wurily ..f nliii. k. Till- wliitLiii Wf UM' uml r«->''.iiiiii>'ii.l i> iiii.lc up ii« f..|l"W-: 'Hi ..iiiKfB ,<( Vnri* (ir.'im, IJ-J ihuuiiU nr«imtf ;{ l.n.l t,, 40 Impfriiil ill..ti. of wiiliT. ■>',.,. X,,t.', ;i nil, I t.) Tliin v.|iiti»ii mUxTi'. ,.iiii»f,i.'i,.ril.v i„ Uu- !i.lin«.' 4tirii.viiiii will »ri'mriill,\ nnicii.t' tnwiir.!- ',1.' |.t .if .Inly. •'.. Aft«'" '"''> '*" wi.'li* rUclil ii|> t,i liarv.'m tiiii,'. ii.>liii{ ••|i.,i...i„'.|" li..r.l.'inix riiijtiir.' af till' f.ill.iwititf .•uniiM.hiliiin : Fi.iir ihuiiiiIm nt limi' ..r m.irp, if inM'i.»piir> o'cj. N.it.. :,) ; ii :i..iii|.l„ Snlpl • ,.f t'opi^T. I:.' (iiin.'M I'arin irri'i'ti, 4ii Iiiip.rinl tMlli.n. ..f whLt. tl. Ik, tii.t (ipru.v on Vfi^- winlv ,lii,v.<. S|,ra.\ iarl,v in the tii.'ri.iiiL'. .,r ,'..iiitti, ii,'e two lirmrn lif«f,.pe xuiimt. I'cmtix.u, -pr.niti^ in miM'ttlwl wmilli.'r, Imt *pruj lli,,r..u«lily pnptii'uliirly iiftcr 11 pori...! uf ri.in. E. Storing Seed Pot'^toe*. 1. Avoid l.nii-iiiir tul.ori' lliriiii(tli I'liri'lcs.. ilitiirina. •J. U«'iti,.v. ull liriii.-cl. ilHiniiKttJ ur fri)»i-ioii.'li,'.l iuIkth l.ofiirr pl.i.itiff potiitnet ill Hl.irimc else il('cn,v in likely In fnllnw .1. Krt.ire tlie p..liiti)e. are lii'inir ..torinl ..vi-r winl ■ 1 wllur!. ,.r otiier st.iriitie plaePK. clean Piune th.irdii^'lily. reiii,,viii(r till refuse iitid il.rt l.'ft over fr..iii lii*t yeiir. Whitt'wasli HiioM. wiilU mill .•>iliti(j« with a fri'-li lime «ii-h .'..nliiitiitin oiip pound i.f lliirMt,.n»> in pvery fifteen LMllons ,.f WH«h. i. Su,ri>ll<- phiees 7,11.. ill. 1 U' ,lry. w. ,1 veiitihited an, I eool. Th«' teitii,.'i;ittire nl' .ilj '0 unif.irm ami not hel.iw ;!:i F'. nii.l tiot uhove '.i>' F. Stor.' p.,tatoer' in hnl,.. not III ha^^'l•< i,rha»rH. ProvidiiiR the tnlHT- w. n- tnatiire when hiirve-le.l. tl,.' loss in st,,ia',-e amuiintiiijr soniilinie'. t.. more than ,iiii -lliinl ..f th.' .Top. will h, jfr utiy, if not entirely reduceil, if tin- al.,ve .'.inilition-, are 'iillill.il. NOTES. 1. Using: Bichloride of Hercnry. Ri.'hloridf of iiier.'ury is 11 dea.lly pois.,n. Whil. In'atinc or drying treat.d potatoes ami wlun .lisp.isiiijr of use.l suliiti.in. keep all tiimi aniinnU ;iHa\. 1 pmiml ,.f hiehlori.Ie will make :.'i»i Iniiu'rial nalluiis .,f s, hili..n. Thr -,lves v.ry slowly. Pri'pnre.l hi.hh.riile, etisnrinjr r;ipid s<)l:i'i.'ii in ei'slly. I'se ITU, I,' hi,'hloriile and reduce it hy |.,iiiiiilinL' t.. a tin.' p,.w.|, r. care U i ... tiiken not to inhale the dust l'r..ni the ch.'iiiieal. Wliei' one p.um.l ha.s U'cn piilveri/. ' divid,' it roii(.'lily into It! (,|ual parts. I'r.ivide as mnn.v ol,| h„ttl.>s ( .1.,, • glass pri- feriihle) ; |iut oiip part .if the powder into eai'li, an. I till them up with lu>- , ,'r. .Shako or ri'll then ahout oceasioimlly until dissolved. The contents of ,' leh b'ltti." ii.lde.l t<. 12* ir:ill"ii- "f wati'r will mak.' n solution reaily for use. ■-Mill irallntw of s.iliitiou will siittlce for the trealni.iit of al.,.ut to husliels of p.,ta- toos. I's.' -..liitii'ii iiiily one, . Korm;ilin vap.iiir ami formalin soluti.in are (>''ic]\ r,'<'oiii- metnh'd. titit hii'hloride of mercury has K'iv.'ii the host results all round. 2. Stable Manure and Artificial Fertilizers in relation to Common Scab. From till' dis.-asi' point of view, sta'ble manure sli.nilil not he use.l l',.r p.'tat'ip.s. This is liki'ly to result in a scahhy crop, whiih 'nt lar;;ily averted hy the u.s.. ,f f.rti- lizers. When then is a lack ..I' humus in the soil, an application ,,f crun.M.'U I'.'at will be f.iuiid upot'ul. This will also retain t\w m.ii^ture in li.irht -.iU. 3. Arsenate of Lead. I'sie "Swift's" nrseti:ite of lead; readily dissolves with stirring. it comes in kegs in form of u soft puste. It 4. Paris Green. One pound paokaKos are ver.v handy. It does not dissnlvo, and sliouhl tie lield in suspension liy constant agitation. Paris grem is a deadly poison. 6. Preparation of Bordeaux Mixture. 1. Slake a quantity of quicklime in one or nioii barrels and fill them witii the paste almost to the top, keeping the lime covered with water — or the lime surface will dry up and be^-ome lumpy and interfere with strainin»f. 2. Prepare a "stock solution"' of Uluestone (Sulphate of Cupper) in such concen- tration that, when using one gallon of (stirred) mixture, 1 pound of the chemical in solution is contained therein. To do this, dissolve 2 pounds of sulphate of copper in 2 gallons of hot wateer. and empty the two gallons into a barrel ; repeat the process until you have one or two barrels full with the "stock solution." If you take fbr use one gallon of "stock solution", you will have 1 pound of copper sulphate. use is as Procedure when making 40 gallons Spray of the Required Strength. To make 40 gallons spray, yuu will require (i pound.^ of copper sulphate witli un "exi'css" of lime, i.e., an amount sufficient tu prevent injury to the leaves. Therefore, have a barrel containing some 33 gallons of water, and add to this 6 gallons of the sul- phate of copper "stock solution" (or pounds of dissolved chemical). Next, add a (juaiitity of lime paste with a shovel and irtir well until dissolved. When dissolved a testing fluid to ascertain excess or deficiem-y of lime. The " test solution ' follows — Diie-hnlf ounce potassium ferrocyanide (poison!) dissolved in one-half pint of water. Fill this solution into a dropping little. Having added and dissolved the lime in the copper sulphate solution, as described above, stir well the contents of the barrel and allow one minute to settle, then drop a few drops of "test solution" into it. If these, on striking the surface, colour the lic|ui(l lirownish. add more lime, stir until dissolved and test again; if the mixture does not . hange colour, the solution contains the proper amount of lime. There is no need to add accurately 4 lbs of lime. Lime will vary in composition, hence the test aliove prescribed is better than relying upon lime by weight. Finally, add to each 40 gallons of spray, the re<|uired