Insecticides. 



25 



TTtust be afterwards diluted. It is prepared by first dissolving 

 the soap, finely divided, in the water by boiling, and then 

 adding it immediately — boiling hot, but away from the fire — to 

 the kerosene. The whole mixture is then churned up while 

 hot with a force pump. After three to five minutes' pumping 

 the emulsion should be perfect ; the mixture w T ill have 

 increased by one-third to one-half in bulk and assumed 

 the consistency of cream. Well made, it should keep indefi- 

 nitely. 



If the water in any locality is hard, it should be softened ; 

 or a milk emulsion formula is suggested instead. For this 

 2 gallons of kerosene are mixed with 1 gallon of sour milk. 

 Heating is unnecessary, otherwise this emulsion is prepared 

 in the same way as the former. The change from a watery 

 liquid to a thick buttery consistency, much thicker than with 

 the soap, takes place very suddenly after from three to five 

 minutes' churning. 



During the growing period of summer, for most aphides 

 and other soft-bodied insects, the emulsion is diluted with 

 from fifteen to twenty times the quantity of water, and for scale 

 insects, with from seven to nine times the amount of water.* 

 In the case of red spider and other plant mites the weaker 

 mixture is used with the addition of 1 oz. of flowers of sulphur 

 per gallon. The emulsions should be sprayed over the plants 

 immediately upon the appearance of the insects. The appli- 

 cation should be just sufficient to wet the plants, without 

 allowing the liquid to run down the trunks of the trees. Care 

 must also be taken that the emulsions are sufficiently diluted, 

 as, if used too strong, they may injure the trees. 



Fumigation with hydrocyanic acid gas of trees infested by 

 scale and other insects has proved satisfactory in America, 

 but a disadvantage is the highly poisonous nature of the gas. 

 Bisulphide of carbon, a very inflammable material, has also 

 been tried with good results on low-lying plants, but this is 

 found more especially satisfactory in the case of insects 

 attacking grain stored in warehouses, and subterranean 

 insects such as the wireworm, etc. 



* It may be noticed that^n England dilutions of less strength — both in the case o 

 the emulsions and the arsenicals — are frequently recommended. 



