No. 5. DEPARTMENT OP AGRICULTURE. 38S 



of petroleum oils in much the same way as kerosene emulsions, ex- 

 cept that phenols are added and vegetable and animal oils are used 

 with potassium or sodium hydroxide as an emulsifier. 



There are now on the market a number of these miscible or soluble 

 oils used against all scale insects and the eggs of many insects pres- 

 ent on the trees during the dormant state. For the lecanium scales 

 they are the only specific. The best of these oils are effective when 

 diluted with water in the proportion of one part to from 15 to 19 

 parts of water. Applications should not be made when the tem- 

 perature is below freezing nor while the trees are wet with snow or 

 rain. Trees are less susceptible to injury just before the buds start 

 in the spring. 



TOBACCO 



The principal alkaloid in the tobacco plant is nicotine, which is 

 a violent poison to most insects and their larvae, and because of this 

 it is one of our most useful insecticides. Pure nicotine is a colorless 

 oily fluid, slightly heavier than water, of little smell, but of an ex- 

 tremely acrid burning taste, even when largely diluted. It is per- 

 fectly soluble in water and is entirely volatile. Commercial tobacco 

 preparations have been on the market for some years and contain the 

 active agent nicotine in the form of nicotine sulphate which is non 

 volatile. The most widely used nicotine preparation is "Black Leaf 

 40" and this is the standard of strength which the manufacturers of 

 other preparations have followed, containing 40 per cent, nicotine 

 which is equal to 51.8 per cent, nicotine sulphate. Nicotine solutions 

 may be used alone or in conjunction with miscible oils, lime-sulphate 

 lead arsenate, soap and Bordeaux mixture, 



FUMIGATION 



Hydrocyanic Acid Gas. The fumes of hydrocyanic acid gas are de- 

 structive of all animal life. This gas may be used to destroy insects 

 wherever the parts to be treated can be enclosed in an air tight 

 chamber. For generating the gas, use of cyanide of potash (98 to 

 100 per cent, pure) 1 oz., Sulphuric acid 1^ fluid ounces, water 3 fluid 

 ounces for each 100 cubic feet of space. Pour the water in a wooden 

 or earthen vessel, add the sulphuric acid and lastly put in the cyanide 

 and leave the room immediately. 



Garhon Bisulphide. This is a colorless liquid having a pleasant 

 odor when pure, but is almost always fetid because of the impurities 

 commercial grades contain. It is very volatile and vaporizes at ordi- 

 nary temperatures quite rapidly. When mixed with air it is ex- 

 plosive and should therefore be kept away from fire. It is very ef- 

 ficacious as an insecticide especially for use in treating stored grains 

 or any infested substances packed in tight receptacles and insects 

 living underground. The gas being slightly heavier than air, dif- 

 fuses into all crevices and spaces below the point at which it is gen- 

 erated. It kills insects by asphyxiating and paralyzing them. Use 

 one pound of the liquid to every one hundred cubic feet of space or 

 one hundred bushels of grain in the bin and ^ lb. per square yard 

 injected into the soil. 



25—5—1914 



