Plant Sanitation, 



420 



[November, 1910. 



the result of long experience has proved 

 conclusively that these measures are 

 adequate to prevent the spread of the 

 disease. 



The treatment of endemic disease is of 

 a different nature. Id this case there 

 is often little risk of the total loss of 

 a crop, or even of the loss of so great a 

 part of it as takes away all profit from 

 the grower. Most frequently the main 

 object is to reduce the percentage of 

 loss due to the disease to a minimum, 

 and thus to increase the profits to the 

 maximum obtainable in the conditions 

 under consideration. Then it is that 

 remedial and preventive measures be- 

 come of the first importance. Total 

 destruction can be but rarely rcom- 

 mended, because it certainly involves 

 the loss of part of the crop, and possibly, 

 that of part of the capital expended on 

 removing dead trees and on replanting 

 others which often give no return for 

 five or six years ; moreover, endemic 

 diseases are apt to affect, to a greater 

 or smaller extent, almost every tree or 

 plant on any plantation where they 

 occur. The position of the mycologist 

 in this case would appear to be a very 

 small one. In reality this is not so. In 

 recommending remedial and preventive 

 measures, he has to consider if the 

 expense involved will gain adequate 

 compensation in additional profits 

 derivable from the treatment. If not, 

 then all he can say is that the existing 

 state of things must be permitted to con- 

 tinue, and in so doing, he allows the 

 planter to run the possible risk of the 

 endemic disease becoming epidemic, and 

 causing the loss of all his plants. 



The conditions which determine if 

 the expense involved in remedial mea- 

 sures is justified by the additional 

 profits obtained are often governed by 

 the interaction of numerous, and some- 

 what delicate, factors. Such are, for 

 example, the general circumstances of 

 climate, the fertility of the soil, its 

 suitability to the crop grown, and the 

 amount of co-operative effort to reduce 

 the disease that is likely to occur in the 

 neighbourhood under consideration. 



In recommending remedial measures, 

 two other important factors must be 

 taken into account, namely, the amount 

 of capital available for carrying them 

 out, and their cumulative effect on the 

 suppression of the disease, Frequentlyi 

 the execution of the best remedial 

 measures, in any given case, involves 

 the outlay of a certain amount of capit- 

 al, and where this is not available, 

 less effective, though frequently much 

 cheaper, measures must be recom- 

 mended, Consequently, it often hap- 



pens that two or three alternative sets 

 of treatment have to be suggested, while 

 the choice of that set which is most 

 applicable in any case, is left to the 

 person who is raising the crop. In 

 some instances, where there is little or 

 no available capital, as in the case of 

 small holders, all that can be suggested 

 by the scientific adviser may be that 

 the disease be permitted to exact an 

 annual toll, as long as this toll does not 

 involve all, or the greater portion, of 

 the profits. On the other hand those 

 possessed of spare capital should bear 

 in mind that the investment of it in 

 thorough and reliable treatment of their 

 crops will often yield a larger return of 

 interest than the money could ever 

 bring if it was invested in ordinary 

 securities, though the risk involved is 

 necessarily somewhat greater. Further, 

 money thus spent not only increases the 

 yield in any given year, but if the treat- 

 ment is continued earns, as it were, a 

 higher rate of interest each year, until a 

 steady maximum is reached, owing to 

 the cumulative effect of the treatment 

 on the suppression of the disease, which 

 suppression continues until the loss due 

 to the disease reaches the minimum that 

 can be effected by that treatment under 

 the given circumstances. Now, it* often 

 happens that a grower desires to in- 

 crease his annual output of produce, aud 

 in order to do so, invests additional 

 capital in new laud ; if, however, he 

 were to invest this capital in carefully 

 carrying out approved measures for 

 reducing the diseases of his crop, he 

 would probably find that his yield would 

 increase to such an extent that the 

 interest on his capital when expended 

 in this way was greater than that which 

 he would have obtained had he invested 

 his money in more land. 



It will probably be clear now, that it 

 is not always an easy matter for the 

 scientific adviser to make suggestions as 

 to the best treatment for any given 

 disease. In addition to the technical 

 difficulties of his work, many considera- 

 tions of a very varied nature must also 

 be taken into account, and it is in deal- 

 ing with these that the co- operation of 

 the practical agriculturist is of the 

 greatest service. Frequently, portions 

 of the diseased material are submitted, 

 for examination by the pathologist, 

 which are forwarded almost without 

 any word of explanation. No informa- 

 tion is given with regard to the field 

 characters of the disease, its extent, aud 

 the general conditions which may affect 

 it ; and no hint is afforded as to the 

 amount that the planter is prepared to 

 expend in controlling it, When this is 



