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GARDENERS' CHRONICLE 



plant palhology appears to be llie only hope of elucidating the 

 matter, and should be forwarded. 



In some cases, however, we have facts which prove that among 

 sorne genera of plants, species and varieties are to be found 

 which are naturally immune to a disease to which other species 

 of the same genera are very susceptible. The most marked 

 case is the Rose and the mildew to which it is greatly subject 

 The incidence of the rose-mildew on the newer races' of Roses 

 supports the fact that immunity and susceptibility are transfer- 

 able on cross-breeding, and the evidence in this direction is the 

 more valuable because the pedigrees of many are known with 

 some degree of certainty. 



The new race of Wichuraiana Roses, which has so altered 

 the appearance of our rose gardens in the last few years, gives 

 the most convincing proof of the fact. These Wichuraianas 

 are descended from Rosa Wichuraiana, crossed with various 

 Teas, Hybrid Teas, Hybrid Perpetuals, etc. The species itself 

 shows an intense degree of resistance to mildew, while this is 

 not necessarily true of the other parents. It is customary to 

 speak of the whole class as being mildew proof, the hard, polished 

 leaves being supposed to be impenetrable by the fungus. As a 

 matter of fact many of this class are badly attacked, and if one 

 looks up the pedigrees of these latter varieties, it will be found 

 that susceptible forms have been used in crossing. Space will 

 not permit us to follow this interesting phase of our subject 

 very far, but before leaving it a few instances confirming the 

 idea will be pi esented. 



We know that the ubiquitous "Dorothy Perkins" is frequently 

 badly mildewed, and we also know that it has not inherited this 

 trait from Kosa ll'ichuraiaiia. its seed parent, but frcim "Mrs. 

 Sharman Crawford," its pollen parent, which is a terror for 

 mildew. 



One of the grandest Rambler Roses of modern times is 

 "American Pillar," a rose with glorious mildew proof foliage 

 ^nd splendid trusses of bloom. This was raised by Dr. Van 

 Fleet from R. Wichniaiaiia and A', sctigcra, neither of which 

 are subject to mildew. 



On the other hand R. iinilliflora. another Japanese species, is 

 distinctly susceptible to mildew, and the fact that "Crimson 

 Rambler" is very subject to it is explained by the fact that 

 luiilhtiora is one of its parents. 



There is no doubt that the banishment of rose mildew from 

 our gardens is to a large extent possible by the production of 

 mildew resisting varieties, but I do not see how any great suc- 

 cess in this direction is likely so long as so many hybridists con- 

 tinue their present system of, so far as mildew is concerned, 

 crossing Hybrid Teas with each other. At the same time while 

 there is no doubt there are many Roses which are more or less 

 immune from disease, there is a considerable amount of mildew 

 which is increased by errors in cultivation, such as over-dosing 

 with chemical manures, carelessness in watering, and by any 

 other conditions which produce a softness in foliage that ren- 

 ders it an easier prey to the fungi. 



The most difficult of plant diseases to combat are those caused 

 by bacteria, the most i)ronounced being known as "fire-blight" 

 on fruit trees, especially the Pear which this disease frequently 

 kills. The disease is caused by a micro-organism entering 

 through the growing points of the twigs and thrives in the 

 soft, succulent parts. Gradually the bacteria work down the 

 stem, kiirng the tissue and causing death of the affected parts. 

 Spraying is of no use, so far as our present knowledge goes, 

 in connection wi'h bacterial disease, the only method which 

 has been partiall> successful is antiseptic pruning. 



The symptoms are that Bowers, young fruit, leaves and twigs 

 turn black and die. It allowed to persist limbs also have sunken 

 cankers form on them and sometimes an entire branch, nr all 

 the branches arj killed. 



Upon its firs* appearance the diseased portion should be cut 

 off together with eighteen inches of healthy growth, first treat- 

 ing the cutting tool with an antiseptic in the form of corro- 

 sive sublimate, one part to one thousand of water, also apply 

 it to the wound made by the pruning. If the wound is more 

 than halt an inch in diameter it should be subsequently dressed 

 with creosote, or tar. .\11 prunings should be promptly burned. 

 It is generally believed that trees are more subject to this dis- 

 ease when they are making excessive growth ; therefore it is 

 advisable to avoid too much stimulating fertilizers. The dis- 

 ease is, however, liable to attack comparatively old trees grow- 

 ing upon poor soil which are making little new growth. Some 

 varieties of pears and apples seem to be relatively immutie, 

 such as the Kieffer and Angouleme pears, and the Jonathan 

 and Northern Spy apples. Fire-blight is found upon the haw- 

 thorn and other similar wild plants of the same family, there- 

 fore thickets and old hedgerows containing wild trees should be 

 cleared away. 



With all the numerdus parasites of the various classes, and 

 there are some which it may not be strictly correct to term 

 Iiarasitic, the most important underlying factor in preventing 



and controlling them is to know their life history, and in this 

 connection the most learned scientists who have" made a life 

 study of them, do not know it all. 



-Xevertheless, as previously pointed out, a close study of the 

 hfe-history of a pest often reveals some weak spot where it 

 is especially vulnerable, and a knowledge of the methods of 

 natural infection and of conditions favoring the speed of any 

 disease, fun.gotis or bacterial, or of the reproduction of any in- 

 ject pest, has and will often lead to effective means of pre- 

 \ention and control. To these ends there is a vast amount of 

 room for experimental work under Held conditions, as labora- 

 tory experiments do not go far enough nor are they in gen- 

 eral sufficiently conclusive. Unfortunately, to give the experi- 

 ments any real value, the first thing is to bring about the 

 existence of the trouble, before any really scientific means of 

 dealing with it can be formulated. However, much has already 

 been learned, ?nd considerable progress made in control and 

 prevention by means of spraying. In bringing this necessarily 

 sketchy lesson to a close a restatement of some of the prm:ipal 

 points will be in order. 



In spraying, thoroughness is very important, so that all parts 

 pf the_ host and every insect upon it are covered with the f5uid. 

 The finer the spray the better, and it should reach the plant 

 as nearly in the form of mist as possible. 



Care should be taken to know whether insect trouble is being 

 caused by cliewing or by sucking insects, or by Ijoth, and the 

 spraying material selected accordingly. 



Do not wait until considerable damage is apparent, but keep 

 a close watch .'o as to be able to start effective measures of 

 control immediately the pest is in existence, and make the in- 

 tervals, when successive sprayings are necessary, not longer 

 than a few days. 



For fungus pests prevention must be first considered and 

 spraying must be commenced before there is any sign of disease. 

 Crops subject ft; disease or pests affecting their roots, tubers, 

 etc., in the soil, should not be grown upon the same ground in 

 successive seasons and the longer the interval the better. In 

 these cases special treatment of the soil, such as lime for "club- 

 root" and sterilizing for those like "root-knot" should be prac- 

 ticed. 



Keep cultivated ground in a sweet, clean condition, and main- 

 tain the available plant food in a state of balance as far as 

 possible, and especially avoid excessive applications of available 

 nitrogen as being likely to encourage rust, mildew, etc. 



In addition to the latter, rusts and other similar diseases are 

 increased by cultivating, or otherwise handling, string beans 

 and some other crops when they are wet with rain or dew ; 

 this practice should lie therefore avoided. 



Diseases can be, and frequently are, transmitted by seeds and 

 until seedsmen can guarantee their seeds free from spores it is 

 well to disinfect them immediately before sowing by a solution 

 of formaline ; this disinfection should also be applied to seed 

 potatoes. 



Keep the garden and its surroundings as far as one's control 

 extends always in the highest sanitary condition, clear from 

 weeds especially those affected with similar diseases to those of 

 cultivated plants, or which act as intermediary hosts for any 

 disease or pest ; burn all prunings and remains of diseased plants 

 at the earliest opportunity, and bury in a pit with freshly burnt 

 lime all other rubbish which will decompose. Do not allow 

 the accumulation of rubbish, especially when pests are hiber- 

 nating for the Winter. 



Do not overlook the question of growing immune species and 

 \arieties, when such are nbtainable. 



There must be a purijose in study, as a path through the woods; 

 without that one wanders aimlessly, 



.Kgain, to study efficiently one must be Interested. Without 

 that it is drudgery. 



Another essential in study is lively .Attention. A thing vividly 

 impressed upon you stays with you. If your attention wanders, 

 shut the book, dii something else, and come back to it later. 



But perhaps the most important element in study is Repetition. 

 That is the secret of mastery. Never mind ; if you have for- 

 .gotten look it up again. 



Another essential matter is to Understand all you read. Do 

 not assume. Do not take things for granted. Challenge every 

 fact. Use the dictionary, the encyclopedia, the teacher. Inves- 

 tigate. Ask questions. Know. Do .not guess. 



Study regularly whether you feel like ii or not. The feeling 

 will come in the grooves of habit. There can be no strong mental 

 fibre without discipline. 



.■\nd when the habit of study is formed, and pursued diligently, 

 you will find it to be one of the iriost unalloyed joys of existence. 



Most persons who have led any sort of intellectual life can truly 

 say : "My happiest hours have been my hours of study." — Dr. 

 I-rank Crane. 



