106 



of the latter. Apply by means of a powder gun, bellows 

 or cloth bag, in such a way that the mixture shall be evenly 

 distributed over the plants to be treated. 



London purple. London purple is also an arsenical 

 stomach poison, and is a compound oi arsenic and lime, con- 

 taining a certain amount of colouring matter. The percent- 

 age of arsenic is smaller than that in Paris green, while a 

 larger proportion of the arsenic present is likely to be 

 soluble. It will be seen from this, that while London 

 purple may be used in a manner exactly similar to 

 that for Paris green, it ought always to be cheaper than this 

 insecticide. It should be remembered, also, that the greater 

 solubility of the arsenic in London purple requires that it 

 should be used more carefully, than Paris green, on account 

 of the greater danger of injuring the foliage of plants. 



The directions for using Paris green apply to London 

 purple, both in the form of aTspray and a dust. 



A r senate of lead. This is also an arsenical stomach 

 poison. It is usually sold as a paste, and in this form can 

 only be used as a spray in a nri^ture with water. Recently 

 however, it has been put in tfhe .market in the form of 

 a powder which, it is stated, can be used in the same 

 manner as dry Paris green or London purple. The 

 advantage attending the use of arsenate of lead results from 

 its great degree of insolubility, and consequently the large 

 comparative safety attending its application to plants 

 A disadvantage which has been experienced in the West 

 Indies results from its slower action as a poison. On this 

 account, it has not been received as favourably by planters 

 as Paris Green and London purple. 



When used as a spray, 2 or 3 R). of arsenate of lead in 

 50 gallons of water will be found satisfactory for the control 

 of most caterpillars. The strength of the mixture may be 

 increased, however, with very little danger of injuring the 

 foliage of the plants. 



The dry form of arsenate of lead may be used without 

 being mixed with lime, as on account of its white colour it 

 can easily be seen on plants treated. 



White arsenic. This is a stomach poison, but it is not 

 adapted to general use. Its greater degree of solubility 

 makes it less satisfactory to apply to the foliage of plants, 

 since on account of the possession of this property it is liable 

 to cause burning or scorching. 



