190 THE HANDBOOK FOR TRACTICAL FARMERS 



This is an extremely poisonous mixture, and should be handled 

 with great care. It is very effective against potato scab. It 

 should not be made in tin vessels, as it corrodes them. 



Crude petroleum. — This is an oily, inflannnable liquid, that, 

 when refined, yields such products as paraffin, lubricating oil, 

 kerosene, etc. A petroleum having a specific gravity of forty- 

 three degrees (Baume scale) is an excellent insecticide for scale 

 insects. In fact, it was used very successfully against the San 

 Jose scale until the lime-sulphur wash was found to be better. 



Formalin.— 



Formula : 



Formalin (40% formakleliyde) , % pound. 

 Water, 15 gallons. 



This is used in treating seed for prevention of such diseases 

 as potato scab. 



Hellebore. — This is a stomach or internal insecticide. It is 

 not poisonous to man, as are the arsenical insecticides, and there- 

 fore is used where there is danger of poison remaining on parts 

 to be eaten. It is often used on currants and gooseberry bushes 

 when the berries are beginning to ripen. This material can be 

 used in the dry form, or as a spray at the rate of two or three 

 ounces to a gallon. 



Hydrocyanic acid gas. — This gas is made by dropping potas- 

 sium cyanide into sulphuric acid and water. The fumes are 

 deadly to all kinds of animal life, and the gas is used only in 

 special cases. As this gas is fatal to human life as well as to 

 insect life, it should be used only by an expert. 



Iron sulphide mixture. — This is a comparativeh^ neiv, but — 

 according to Circular No. 58 of the Bureau of Plant Industry, 

 United States Department of Agriculture — a very promising 

 fungicide. It was tried on apples especially, and gave splendid 

 results in preventing fungous diseases. It also proved non- 

 injurious to the fruit. In preparing this fungicide, it is recom- 

 mended that a self-boiled lime-sulphur mixture be prepared, as 

 hereinafter described; except that ten pounds of lime and ten 

 pounds of sulphur are used. The mixture is diluted to forty 

 gallons, and then three pounds of iron sulphate (copperas) 

 dissolved in about eight gallons of water, is added. 



Kerosene. — This is an excellent contact insecticide. The 

 merest particle of it, coming in contact A\^th any part of the 

 anatomy of an insect, is fatal. Pure kerosene, however, will 

 ordinarily burn the leaves of plants, consequently it is only 

 recommended to be used in the pure form when trees are dor- 



