18 The Principles of Fruit-growing 



life-histories of the various pests, and can point out their 

 most vulnerable points, and may even devise general means 

 for their eradication; but the final application of this knowl- 

 edge is a local problem, which each man must work out for 

 himself. Laws are only secondary means of keeping in- 

 sects and diseases in check on a man's own farm; they are 

 chiefly useful in providing a way of controlling the man 

 who is neglectful, ignorant, or devoid of public responsi- 

 bility. They are most applicable in those cases in which 

 disease is more or less permanent or perennial, and in 

 which there is no practicable recourse but to destroy the 

 plant or the part affected. Such troubles are peach ye^ 

 lows and black-knot of the plum and cherry. | A law can- 

 not be enforced unless public sentiment is behind it, and 

 when public sentiment is completely aroused the law may 

 not be needed. Yet a good law is one of the best educators, 

 and if properly enforced may save an industry, but it 

 must be remembered that the final recourse is always 

 greater knowledge and enlightenment on the part of the 

 individual growers. 



That the grower may not expect so much of the opera- 

 tion of laws as to lessen his own activity, let him consider 

 the practical difficulties in the enforcement of them. It is 

 practically impossible to detect the eggs of insects or^ 

 spores of fungi on large numbers of plants, and there are 

 many natural and uncontrollable ways in which the para- 

 sites may spread. A law may very properly require that 

 "whenever any trees, plants, or vines, are shipped into this 

 state from another state, every package thereof shall be 

 plainly labeled on the outside with the name of the consignor, 

 and a certificate showing that the contents had been in- 

 spected by a State or Government officer, and that the trees, 

 plants, or vines therein contained are free from all San Jos6 



