REMEDIES FOR INJURIOUS INSECTS 245 



great ravages. The infested district was cleared without labour 

 or cost in about two years. 



The treatment of the fluted scale by the importation of 

 Vedalia is now widely recognised as one of the most bene- 

 ficent applications of scientific method to the alleviation of 

 public ills. 



REMEDIES FOR INJURIOUS INSECTS 

 Washes and Sprays 



These are either laid on with brushes or hand-sprinklers 

 or spraying machines. The most effective and far-reaching 

 machines are of American construction. 



Spraying is sometimes the only expedient that can be resorted 

 to, as, for instance, when the insects attack the leaves of high 

 trees. Its effect may be greatly diminished if the leaves throw 

 off liquids easily. The destruction of insects by direct contact 

 is not so much aimed at as the poisoning of their food. There 

 is often serious risk of injuring foliage, young shoots, or fruits. 

 The strength of solution can seldom be precisely given, as 

 much depends upon the plant affected, the insect which infests 

 it, and other variable circumstances. The following insecti- 

 cide solutions have proved particularly useful in American 

 practice : — 



I. Arsenical solutions. — For detailed and practical instruc- 

 tions on the use of arsenical and other preparations the reader 

 may advantageously consult C. L. Marlatt's "Important In- 

 secticides" (Farmer's Bulletin, No. 127). This is issued by 

 the United States Department of Agriculture, and distributed 

 free in the United States. A condensed statement of part of 

 this pamphlet follows. 



The chief arsenical compound in common use is Paris green 

 (aceto-arsenite of copper). Scheele's green (copper arsenite) 

 and lead arsenite are less known. Mr Marlatt points out that 

 Scheele's green is a finer powder than Paris green, and there- 

 fore more easily kept in suspension; it is less harmful to foliage, 

 quicker in action, and costs only half as much. Lead arsenate 

 is safer for use on delicate plants than any other arsenical. 

 The fresh-prepared mixture adheres better to foliage than that 

 which has been dried and repulverised. 



