132 Control of Parasites 



indifferent to such efforts, and as long as a few breeding 

 places are maintained by private indifference or lack of 

 public spirit, all efforts can be only partially successful. 

 Unless laws and ordinances compelling everybody to keep 

 his premises free from these nuisances are passed and en- 

 forced by fines and otherwise, we shall always have these 

 pests with us. 



In Germany, such laws of general application and ordi- 

 nances for given localities, especially for combating insect 

 pests in forests, have been in vogue for a long time. It is 

 only by constant vigilance and by the absolute enforcement 

 of such laws that the Colorado potato-beetle, again and 

 again imported, has been kept out of Prussia. 



Although in street and ornamental plantings the methods 

 of combating insects are naturally different from those 

 which are employed by the forester, the tree-warden can, 

 nevertheless, be greatly benefited by knowing those of his 

 brother arboriculturist in the forest. 



The forester, being chiefly concerned in economic prob- 

 lems, considers first the question of economy and of rela- 

 tive cost; he must balance the advantage in expenditure for 

 combating an enemy wdth the saving in ultimate revenue 

 resulting therefrom: he will, therefore, often let matters 

 take care of themselves and suft'er the damage, if he can see 

 that it is not too serious. The tree-warden, who has no 

 economic object to attain, has no basis for calculating what 

 he can aft'ord to pay for the luxury of shade and beauty. 

 Yet as he will want to a^'oid any unnecessary expense, he 

 should follow the same line of reasoning as the forester in 

 judging of the necessity and method of combating a pest, 

 although he may come to a different decision. Especially 

 in parks and large country estates the question of practi- 

 cability may become serious. 



