July 6. 1912 



THE GARDENERS' MAGAZINE. 



507 



ENGLISH LEGISLATION AND 



PLANT DISEASES. 



(Concluded from page 490.) 



Survey of Plant Diseases. 



Now it is laid down in the American Goose- 

 berry Mildew Order and in the Wart Disease 

 of Potatoes Order, that in defining the limits 

 of the infected premises only that part of 

 any garden or other holding is to be included 

 on which disease exists or has recently ex- 

 isted. The areas, therefore, are small, 

 seldom exceeding three acres, and in most 

 eases much less. One large fruit farmer, 

 therefore, may have several infected premises 

 his occupation, and, as a matter of fact, 

 are so^nie times ten 'OT 'twelve (Such 

 registered under the name of one oc- 

 I have laid what may seem to some 

 stress upon this point, which appears 

 at first sight a trivial one, because it is 

 here that the foundation-stone is laid of the 



in 

 there 



places 



cupier 



undue 



affected by disease, and an expression mea- 

 suring the intensity of the attack through- 

 out the garden. But if this report is to 

 be of anv use it must be based upon an 

 agreed scale of degrees, and must not 

 be merely the personal impression of the 

 inspector. 



Scheduling: Diseases. 



The me^ure of the extent of the disease 

 is a comparatively simple affair. Given that 

 the infected premises cover three acres or 

 one acre of gooseberry bushes— and each re- 

 port must in the first instance give the 

 approximate area scheduled— the inspector 

 has merely to ascertain the proportion 

 affected. A scale of five degrees is taken, 

 and the words "very many/' "many/* 

 "common," "few," "very few," arc used to 

 signify the numl^er of bushes attacked, llius 

 if less than 10 per cent, of the bushes are 

 mildewed, the report says "very few'*; if 

 between 10 per cent, and 30 per cent., "few." 

 " Common " implies between 30 per cent, and 



sious of disease, viz., the extent and the in- 

 tercity it is possible to calculate with some 

 accuracy the amount of disease present over 

 anv given area, from a parish to the kingdom, 

 to co'inpare one district with another, and one 

 year with another. It is the best, if not the 

 only way of estimating the effect of wide- 

 spread influences, such us the weather and 

 the character of soil on the spread of disease, 

 and it is a very usv4*ul method of studying 

 the general effect of any remedial 

 that may be adopted over large districts. 

 Finally, it is the only accurate way of exhi- 

 biting to I'oreij^n (ioviMiniKuts or private 

 traders \\lu> wi^h to asnitain the 60urc?J 

 from wliuk nursery stock or other produce, 

 for ]Mirpof.^ s of propagation, can be obtained 

 with a re;usonab!e a<=^urance of e8ca))ing in- 

 fection. The system is as yet only in its 

 infancy, and it ^is anticipated that as it is 

 applied to new diseases and continued for a 

 loi ger period it will be found useful in draw, 

 ing attention to -acts that would othtrwi,-- 

 Ih» overlooke<l. and i!ia1<'rially a^-^ist in <lra%\- 



DEYIXG TOBACCO LEAVES AFTER GATHERING. 



of Plant 60 



whole structure of the Survey 

 Diseases in England which the Board have 

 been trying to build up. The system on 

 which this survey has been planned has 

 already been fully described in the annual 

 reports of the Intelligence Division of the 

 Board of Agriculture and Fisheries, Part II., 

 but as it is intimately bound up with the 

 subject of this paper, it may perhaps be out- 

 lined again. In the first place, it is ob- 

 vious that the first step to be taken in making 

 a study of any plant pest which it is pro- 

 posed to eradicate is to ascertain the area 

 over which the pest has spread. Without an 

 adequate knowledge of the "extent" of the 

 attack in every county, and in every garden, 

 no progress can be made. But it is equally 

 important to ascertain what is the " in- 

 tensity " of the attack in each place, since 

 this alone can give any true conception of 

 the amount of injury done. Every report, 

 therefore, that is sent in to the Board re- 

 specting an outbreak of American Goose- 

 berry Mildew must contain a record of the 

 extent of the infected premises that are 



; many, 

 very many. 



60 per cent, to 80 

 80 per cent, to 100 



per cent, 

 per cent. ; 

 per cent. 



The measure of the intensity of the disease 

 is a much more difficult affair, and implies 

 a study of the development of the disease 

 from the moment when it first becomes ap- 

 parent on the plant to the state when the 

 bush is either dead or of so little economic 

 value that it is uprooted and destroyed by the 

 occupier. The number of degrees m the 

 scale of intensity is, however, the Bame as in 

 the scale of extent, the words eelected being 

 "very slight," "slight," "general," bad, 

 and "very bad." The symptoms whicli jus- 

 tify the inclusion of any case m each degree 

 vary with the disease under consideration, 

 and are, of course, selected in an arbitrary 

 manner. They have been fully 

 the annual reports already referred 1.o, and 

 need not be explained again ^^^^lly as a 

 short explanation is attached to the Maps of 

 Disease shown in the Exhibition It is suffi- 

 cient to point out that by collecting a series 

 of reports each of which records two dimen- 



of epide- 



inff conclusi Mis as to the prog 



So far only those Orders of the Board have 

 been described which deal with diseat^^s that 

 are more or less firmly established in this 

 country, and that will require a long and 

 natient course 



indeed that can ever be accomplished. Such 

 disea^ses are, of course, chiefly a matter ot 

 interest to the Government of the country 

 concerned, and the farmers and fruit-growers 

 that are affected. 



Insects to Guard Against. 



Orders that relate to the third class of 



po«ts are of a wider interest, and affect not 



only the home grower but the foreign trader 



who wishes to place his goods on the Eng hsh 



market, and to a certain extent the Englisli 



nurseryman who wishes to dis]K>se of his 



stock abroad. It hiv? already Ihhmi exijlamed 



that the pesta referred to are those which are 



either nonexistent in England, or have only 



recently been introduced. But, as stated it 



r„ +i,r,f fii*>rfl i« a. fourth class 



