Tobacco Insecticides 341 



pour into a barrel or tank and make up to fifty gallons. Keep well 

 agitated. Very effective against peach-scab and brown-rot. Several 

 other formulas have been used: 10-10-50 and 5-5-50. Arsenate of 

 lead can be used with this mixture. By using boiling water and allow- 

 ing the hot mixture to stand for half an hour, a stronger spray mix- 

 ture than the above can be secured. It cannot be used safely on 

 peaches, but has been used successfully on grapes for surface mildew. 

 The addition of sulf ate of iron or sulf ate of copper, one to two pounds 

 to fifty gallons, has been used for apple-rust. 



Tobacco is one of our most useful insecticides. The poisonous 

 principle in tobacco is an alkaloid nicotine, which, in the pure state, 

 is a colorless fluid, slightly heavier than water, of little smell when 

 cold and with an exceedingly acrid burning taste even when largely 

 diluted. It is soluble in water and entirely volatile. It is one of the 

 most virulent poisons known; a single drop is sufficient to kill a dog. 

 Commercial tobacco preparations have been on the market for many 

 years. The most important of these are black leaf, "black leaf 40," 

 and nicofume. 



"Black leaf" was formerly the most widely used tobacco extract. 

 It contains only 2.7 per cent nicotine and has now been replaced by 

 the more concentrated extracts. It is used for plant-lice at the rate 

 of one gallon to sixty-five gallons of water. 



"Black leaf 40" is a concentrate tobacco extract containing 40 

 per cent nicotine sulf ate. Its specific gravity is about 1.25. In this 

 preparation the nicotine is in a non-volatile form, it having been 

 treated with sulfuric acid to form the sulfate. "Black leaf 40" is 

 used at strengths varying from one part in 800 parts of water to one 

 part in 1,600 parts. It can be satisfactorily combined with other 

 sprays, as for example, lime-sulfur solution, arsenate of lead, and 

 the various soap solutions. When used with water, about four pounds 

 of soap should be added to make the mixture spread and stick better. 



"Nicofume" is a tobacco extract containing 40 per cent of nicotine 

 in the volatile form. Strips of paper soaked in this preparation are 

 smudged in greenhouses to destroy aphids. 



Tobacco is also used in the form of dust for the same purpose. It 

 is especially valuable against root-lice on asters and other plants. 

 Tobacco extracts can be made at home by steeping tobacco stems 

 in water, but as they vary greatly in nicotine content and are some- 

 times likely to injure tender foliage, it is better to buy the stand- 

 ardized extracts. 



