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D D D lOx 14x IlK 22x 26x SOx y 12x 18x 20x 24x 28x 32x Th« copy firmed h«r« Km bMti rvproducad than» to th« g«n«rosity of: Library Agricuitura Canada The imagM appMring hara arm tha baat quality poaaibia eonaidaring tha condition and lagibiiity of tha original copy and in icaaping with tha filming contract spacifieationa. Original eopiaa in printad papar eovara ara filmad beginning with tha front eovar and anding on tha laat paga with a printad or illuatratad impraa- •ion, or tha back eovar whan appropriate. All othar original eopiaa ara filmad beginning on the firat paga with a printed or illuatratad imprae- aion, and anding on the laat page with a printad or illuatratad impreaalon. The laat recorded frame on eech microfiehe shall contain tha symbol -^ (meaning "CON- TINUED"), or the symbol V (meaning "END"), whichever appilaa. Mapa. platea. charts, etc.. mey be filmed at different reduction ratioa. Thoae too large to be entirely Included in one expoeure are filmed beginning in the upper left hand comer, left to right and top to bottom, aa many framee aa required. The following diagrama illuatrato the method: L'M«mplair« film* fut rtproduit grica k la gAnAroait* da: BiUiotMqiM Aflrieulturt Canada Laa imagaa auivantaa ont 4t« raproduitaa avac la plua grand soin. eompta tanu da la condition at da la nattat* do I'axampiaira fiim«. at an eonformit* a««e laa eondltiona du contrat da fiimaga. Laa axamplairaa originaux dont la eouvartura tn paplar aat imprim«a sont fiimte an commandant par la pramiar plat at an tarminant soit par la damiira paga qui comporta una amprainta d'Impraaaion qu d'HIuatration. soit par la sacond plat, saion ';u!t--ii I'l •. tiui Km'KKIMKM.M <)Tr*««. V, Kami . I'l'iinrv li'U .1 il OusuAU:. Ksq., B.A|[r.. i Piraetor, Diimiiiioii Kx|>vriiiii'iitai Kuriim. 1 IVpnrtment of Agricultiiri', I Ottawa. I Sill,— 1 beg to miDtiiit for ymir iip|iri.viil ii cirtiilar prt'i . .i liy Mi .1 W I liasthaci, B.Sc, Chief Awixtunf, Divisi.m of Uotiiii.v. Jciiliiijr with Towiliry Soiib ot I I'otatoei (Spongotpora nublerrama (Wallr.) Joliris.). It hu» ln«ii pri-piind at my I ro<|UMt to meet the tipcd for informiition on this ilisoasc. which hus ri'cnitly bi'oomr ; of couRiderable importance in thi.< rountrj' nn account of the new rcKuintioiis puniet! J by the United Stntoii authorities, confrolliinf ihe importiitinn of po'Mt.nii into thai I ''ountry. Mr. Kaitham, from his oxperiencc in iilunl pathoioKj- ami hi^ ''Uw Rtiiil,'- jf th* di»ea>ie, is well qualitioil to fiirnich giieh iiifornuition and advice, nnd I entirely nirre*- with the Dtutoments and recoinniendatinns made in this circular. In view of the necessity for an educational cninpniifn nnionast tlic ))otut<> irrower'- ;of the Dominion, I would recommend it* inimedinte publicntion h« •• Farmers' f'irr'iilar j No. S '■ nf the Division of Botany. I have thi' lioiiDiir to be. »ir. Your obedient servmit. H T. GUSSttW, Doyriiriidii lUtltitiiti POWDERY SCAB OF POTATOES. Willi the iiicrcniiiiiK iniixi •., of tl< rH.uto - r«|> in ("iiii«iiii. the »ul>i.vt of th«> ili»ttt»«i» to whii'h thii crop ii liu.le bei" u. il*,, jnorc impi)rtuiit. iml thin for netirfc. rprt«im«. In the flrit plm-e. tho arc* i . ,tmi U the crop twitiK tfrwiinr, any diKk^s i«l>fclitlly if opidpmic in rhuranter, inHifU * /roatrr total lixa. Airniii, |K,t4it.. I'elrto I litiiiR doner touetlior. thcro i« more likclihoo* ,.f di^rMiie sporca beliiii carrii-d fr.ni on^ i Held to the other by the wind. •* in the ea»e of Lute Bli«ht. or in thn toil adhcrii.K Ui iinplomentj, etc., in the caie of certain other dinoaiio*. Where potutoen ocmr ii,. r« t". • liiently in the rotation, there ii alio more iluuKer of the toil liwimiing Mri.,uily infoptod with the serma of certnin pcniateiit toil diaeaM'*, tinlea* apciial care it l..kfi, I in the le' n nml .liiinfectiim of the tnbern imod for plantiiiK- I.n«tly, whi n a I «iirphii ' ;i t i« jtrown «nd shipped to other localitiea. di*eaiea may lik"wi«e be< imf I »radiiai) u ■ minated o?er wide aroai, Mpo- ipcration, methods directed towards the eradication of the disease. i Tho Federal and Provincial Departments of Agriculture are willing to do all in ^ leir por:er to instruct the farmers to recognize the disease, and to take the stip» ^cccssnry to stamp it out; but the responsibility for the carrying out of this adviet XMth m wUehThe use of the microscope may be necessary for -'"P>«*'=;'^'*".'"^'^- „^"/"„^^," Tning a topical case we find that the skin of the potato is raised up '» l-'^-^'l"--' °;^^• ,,• .• i ♦ 1 = /Qoo TTifl. 2 1 These have an even outline, and when young •notg of ten coalesce to form one large scab. A cie of Common S.ab compare.1 with this stage of Powdery Scab differs ,n the more i^^llar ISin of the spots, and by the surface being rough, irregnlar and Trky, 7'^mItimJ^forming an irregular pit in the surface of the tuber instead of being smooth and even. ■ „..;i.. As the Powdery Scab spots reach maturity, the skin covering them is caMb broken Sien thereTs disclosed a mass of greenish or brownish powder, t'om wlu thf df^ase tekes the name of Powdery Scab. On rubbing away this powder, it will h^ fo^r^itt^l pustui; is bounded beneath by a smooth brownish -mbrane which Sits it Site sharply from the normal tissue. In potatoes .-^-h have b^n much rubbed in transportation this may be the only remaining md cation of the dl^ease. I^thl ease of Common Scab there is no powdery mass filling the interior of the sc.l, .pot but^i^y a superficial irregular layer of corky cells. There is also no definite layer separating it from the underlying healthy tissue. The powdery mass, under the microscope, is seen to consist of innumerabU- gi;ain- or balls of an iVregulariy rounded form, each of which is made up oi a largo nun,ber Jet mini ro^nd spores, and hence termed a " spore-ball." Under the n^h cou^ ditionT (moisture, warmth, etc.) the membrane enclosing each spore ma^^ ^Jj;'"^ the living contents of each individual spore emerge as a so-called J7'"'fl"^^; This swafm-spore Possesses, to a certain extent, the power of moving about by its ow . efforts and shoul.i it come into contact with a young potato tuber may effect a,> SrTn'ce into one of the more superficial cells. Within the cells it undergoes cert ai. changes wl L at the same time the cell is stimulated to more rapid mult.plKation lo thTt from one or several neighbouring infections a mass of cells is formed wh.c projects as a small wart or pustule from the surface of the tuber Each coll of th nustSe will contain one or more of the Powdery Scab organisms which have de^e^ope<. from the iwarm-spores first mentioned .and ultimately each of these organism changes into one of the spore-balls with which we started. In the mean ime the livi, contents of the potato cell have been used up by the parasite withm, the cell breaV do^ and the interior of the pustule becomes filled with the powdery mass of spoi. balls previously described. A little consideration of the lift-history of this parasite will enable the reader tn see how readily the disease may be spread, through ignorance. When a crop of pota- toes affected by it has been dug, it is obTious that, in the process, many of the scab spots will have been broken open and countless numbers of spore-balls scattered in the soil, on the implements, on the shoes, hands and clothing of the workmen, and in thii> way may be spread from field to field. We have not, as yet, all the knowledge we desire regarding the behaviour of these spores, in particular as to the length of time for which they may remain dormant in the soil and then produce infection of a potato crop planted therein. Probably, however, considering what wc know of similar diseases, they retain this power for a number of years. Until, therefore, we are in a position to say definitely how many years the disease may persist in the soil, it will be found necessary to avoid growing potatoes again on any land which has once shown this disease. Although the disease is only known to attack the underground parts, the vine.-- and any refuse from an infected crop should bo raked together and burned. This will get rid of any adhering spores of this disease and, incidentally, of certain other pcstt. The implements, containers, etc., used for such a crop should be disinfected according to instructions given at the end of this circular, before being taken to other fields, or used for other purposes. Since no other crop is known to be liable to attack, the infected laud may be put into any crop thought suitable. However, when the disease is very bad, and spores arf correspondingly numerous in the soil, it is conceivable that the wind blowing over the surface of the field may catch up quantities of the spores and deposit them on land previously uncontaminated. Whore a crop is put in, there is also more danger of the germs of the disease being spread on implements if care is not taken to clean them thoroughly before taking them from one field to another. For these reasons we strongly recommend that, wher- ever possi'le, the land should be seeded down with gi-ass or clover — a "nurse" grain crop may be used — and left in meadow or pasture for a term of years. Still bearing in mind what has been said regarding the power of the spores tc spread the disease, we must next consider the proper method of disposing of the affected crop. The worst possible means of so doing is to sell it for seed purposes to other irrowcrs. This is the most effective way of spreading the disease. The affected crop is not injured for consumption except, according to our experi- ence in Canada, in very rare instances. If the crop affected is a small one it may he used for domestic purposes; if larger, a part of it may be fed to stock, and it may lie desirable to add a number of pigs to the live stock kept, if the quantity to be con- sumed is large. No potatoes from an infected crop should be fed to stock without being cooked, for there is danger that the spores may pass through the difiestive organ? of an animal and still retain their vitality, thus rendering the manure a mean? ; (if spreading the disease. The affected crop should be stored in pits or on the field, or, if brought indoors, should be placed in a cellar separate from the sound potatoes, with which it should not lie allowed to come in contact. Similarly, any container used for the handling of infected potatoes should be kept for this purpose only. To carry a quantity of infectr^d potatoes in a basket, and then to put sound potatoes, perhaps subsequently used for seed, in the same basket, would be to undo the effects of previous care. If the potatoes are peeled for cooking purposes, the porings should be burned or boiled, and on no account thrown out raw to the manure-heap. If it is intended to j bake infected potatoes, and they are washed first in a bucket or barrel of water, and ;' this water then emptied out in the barnyard where it can drain away to the manure- lieap, or be carried about on the feet of poultry, the seeds of a fresh crop of disease are being distributed. 10 It must not be foreotton that these observations apply also, though in a lis- doffreo, to the apparently souiil tubers frnm nu affected crop, as well as to tiibfrf^ actually diseased. When nil the infected crop has been finally disposed of. the bins and cellars uscil for the storngo of it slioiild, preferably, be washed down with a disinfectant, or at least lime-washed with fresh lime. Containers, such as baskets and sack', should be disin- fected or burned. There is at present no legal restriction on the sale of infected potatoes. It will be realized, it is hoped, that a farmer who disposes of potatoes from an iufei'tcd ero)) without informing the purchaser that the disease is present in it, is guilty of n serious offence iigainst the community. Should it be found that some growers are suiiicientl.v unscrupulous to do this, it will probably lead to the enforcement of a penalty in sucli eases. So far, we have considered only the procedure to be followed in disposing of an affected crop. Wo must now consider how the crop came to be diseased. In all cases tiiis is due to infected soil, the only parts of the plant capable of receiving infection being those underground. We have already mentioned some of the ways in which the soil may become infected, but we cannot too strongly emphasize tlie fact that the chief means l>y which the disease is spread, is by the careless or ignorant planting of diseased tubers, or those from a diseased crop. This is, in fact, the way in which nearly all disease in the potato crop originates each year in this country. It is important, therefore, to select for seed only tubers from a healthy crop. If such seed must be purchased it should be done under a certificate or guarantee to this effect. Apparently sound tubers from an attacked crop should not be planted, although, if carefully treated with formalin or corrosive sublimate to destroy germs adhering to the surface, the danger is perhaps not very great We have evidence, however, that a tuber so slightly affected as to give little or no external evidence of the fact, may yet contain the living parasite within its cells and, if planted, introduce the disease. Therefore, the only absolutely safe plan is to use " seed " only from a perfectly sound crop. Amingements are being made whereby responsible officials of the Dominion and Provincial Governments will, upon request, inspect the crop or any portion of such a crop as desired by the grower, and give a certificate that this is free from disease and fit for use as seed. Having secured sound seed, it should be planted in land which has never borne a crop of potatoes affected with the disease. In view of the fact that nothing is known of tho presence or distribution of the disease in the past, it is impossible in most cases to say whotlier previous crops have been infected or not, and therefore tho safe plan would bo to use only land on which potatoes have not been previously grown. With our conditions hero in Canada, we should be able to do this without undue hardship. Lastly, there are certain precautions to be taken with regard to implements. In some districts it is customary for a planting-machine to be hired, and this machine goes about from one farm to another. If such a machine has been used to plant diseased potatoes on one farm, and then goes to another without having been cleaned and disinfected, it is obvious that every possible facility is being given for spreadinp tho dise:ise. We have evidence to show that this has actually taken place. It is, there- fore, roi'oramended that farmers should cither plant by hand, use their own planter, or insist on proper disinfection of the machine before it comes on to their land. 01 course, if all growers follow carefully the instructions hero given with regard to thi selection of "seed," one thorough disinfection of the machine at tho beginning of th( season might suffico, but as the negligence or ignorance of one grower in putting: infected " seed" through tho machine might bo followed by the spread of the infcctioi. to a larse area of new soil, it is best to take ovory possible precaution. 1. Tuber affected with Comtnon ^>cab. 2. Tuber showing a inilH attack (»f I'owdcry Scab. The puHtules are niostlv smftU and isolated. 3. A more sicriims form of the disease. The soabt* are con- Huent and cover a larf^u nrouortion of the surfact*. 4. Hhows different apiM^arances prewnted by the pusti'lew. Thvie inaikea + nave the coveting membrane still intact; in those niurketl || the u>erabrane has jiiMt been broken, while at O the niasa of »{>ore-balU is becoming broken up and the 8i»ore-ball3 scattered. 5. A much deformed tu!>er showing a veiy bad, but fortunately rare, fnrm of the dixeam. {From ortgincU hhotoyraphi hy H. T. flU$iow.) li DISINFECTANTS. (1) For teed tuher^. — These arc not to be relied upon to make diseased tubers tii for planting, but only to destroy spores adhering to the surface. If souml '• seed" i- sclected and disinfection practised, the chances of introducing Powdery Scab, Commor. Scab, Bhizoctonia and certain other diseases are much reduced. (a) Formalin (Formaldehyde). — The substance, as purchased, should be guiiruii teed a 40 per cent solution of formaldehyde. A solution of this is prepared at the rate of 1 pound of the commercial substance to 30 gallons of water. The potatoes t" be disinfected are soaked one and one-half to two hours in this solution before cutting. They are then taken out and spread on a clean floor, or on the grass, to dry. They may then be cut, if desired, and planted in the usual way. Whatever is to come into contact with the tubers a^cer treatment, should be disinfected by being wiped down with, or immersed in, the same solution or, preferably, one still stronger. The solu- tion may be used repeatedly, as it does not become weaker. There should alwnyp. however, be sufiScient liquid to cover the tubers to be treated. (&) Corrosive Suhlimate (Mcrevric Chloride). — This is a very powerful disin- fectant, having given us better results than formalin with some organisms, notably Rhizoctonia. It is also very convenient, since it can be purchased in tablets of siich a size that one, dissolved in a pint of water, makes a 1 to lOOO solution by weSitht. Its chief drawback is that it is intensely poisonous, and tubers treated with it cannot be used subsequently for food, as may be done, if desired, with those treated with fonnalin. The solution also corrodes metals, and must, therefore, be prepared in n wooden, glass, or earthenware vessel. For most purposes as a disinfcctaat, a solution of one part by weight in 1000 of water is employed, and this strength is commonly recommended for seed treatment, the seed being soaked for an hour and a half. Wc have, however, obtained better results from a 1 in 2000 solution used for throe hour?-. The same precautions as given for formalin regarding subsequent contamination should be observed. The solution, however, becomes weaker with use owing to the absorption of the corrosive sublimate by the potatoes. The same solution should, therefore not be used more than six times. (2) For washing baskets, bins, implements, or sterilizing hags, containers, etc.. the solution of corrosive sublimate (1 to 1000 strength) is reliable. Where, however, there is thought to be any danger to animals from its use, a strong solution of form- alin, one pound of the commercial substance to one gallon of water, may be employed. While formaldehyde solution has a powerful local action on animal tissues, hardening the skin and irritating the mucous membrane, it is not poisonous in high dilutions. Furthermore, formaldehyde is a gas, and when the liquid ha« evaporated, the formal- dehyde has pas.sed off into the air, not being left behind as in the case of corrosive sublimate. For seed drills or other metal implements, which the frequent use of cor- rosive sublimate might corrode, the strong solution of formaldehyde may be employed, or a five per cent solution of carbolic acid. Cellars may be lime-washed with fresh quick lime, and the floors treated with chloride of lime (bleaching powder). 13 1 sriMMARY OF RKCOMMENDATIOXS FOIl CONTROl, OF PO\VDP:UY SCAR 1. Use only "' fOod " from a crop free from thi^ iliseasc ± Disinfect such " secj " to destroy any stray disease gcnns. 3. Use land known to be free from the disease. In most iircas lln- will have to br land not previously planted to potatoes. ■t. Do not plant potatoc again in land which has shown tliu iii-i:i-c. If [lossible aeod 9uch land down to grass. 5. Isolate the crop from any field showing the disease, and take all possible pre- cautions to avoi