ADDITIONAL PAPERS. 239 



can be killed by poisons sucb as Paris green, arsenic-salts, 

 etc., and can be put on the plant before the insect appears, thus 

 acting as a preventative. 



For the sucking- insects we must use something which 

 will kill by contact, and the material can never be used as a 

 preventative for that reason. Emulsions are usually used for 

 the more tender ones and the lime, sulphur, salt mixture is 

 used for the San Jose Scale, which is probably the most hardy 

 one. Kerosene emulsion is made of soap and kerosene. The 

 soap is dissolved in hot water and then the oil is added, and 

 the mixture thoroughly churned for four or five minutes 

 until the whole is a thick, milky mass. Upon cooling, this 

 should be a thick, glutenous mass. Soap is an insecticide 

 in itself, varying with the strength of the soap. Kerosene is 

 also an insecticide, but it is so strong that it burns the plants 

 and must be diluted. It will not mix with water, but by 

 making an emulsion it can be used with water. The soap 

 separates it and thus it is diluted in the water. 



Many people think of Bordeaux mixture as an insecticide, 

 but it is not. Why? Because it only contains lime and cop- 

 per sulphate, and neither are present strong enough to kill 

 or poison insects. But by adding Paris green or some other 

 poison which will readily mix with the solution it may be used 

 as an insecticide and fungicide. You have often heard this 

 saying, "Never use an emulsion with Bordeaux." If you 

 ask why not, you will probably be told they will not mix. 

 This is not strictly true. Less than three years ago, up at the 

 college, we put together normal solutions of Bordeaux mix- 

 ture and kerosene emulsion and they mixed easily as far as 

 we could see. There was no combination that prevented the 

 use of the mixture in the pump, nor did the mixture quickly 

 separate. But after standing for some time it separated, 

 part settling, and probably it was the emulsion which rose 

 to the top. After standing two or three days the mixture 

 precipitated. 



The reason why we never use an emulsion with a fungi- 

 cide is that it is not necessary. At the time the fungicide is 

 applied the insects may not be present, and it would be of no 

 value at any other time. 



