264 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 5 



tion made by steeping 5 grms. of smoking tobacco in 15 cc. of water 

 was fairly successful against scale insects. Tobacco water and tobacco 

 smoke have long been employed against aphids and other delicate 

 insects wherever the vapors can be confined, as in a greenhouse. Boil- 

 ing of tobacco in such enclosures is as effective and often less injurious 

 to the plants than the older methods of syringing a decoction or of 

 fumigation by burning. 



Tobacco, as an insecticide, may be used in several ways and forms: 

 as (1) a liquid spray of a decoction made by soaking the stems, (2) 

 a powder for dusting on plants, and (3) a fumigant, the fumes being 

 produced by the burning of the stems or powder. To these might also 

 be added the various commercial tobacco extracts and nicotine prep- 

 arations now on the market, which may be used both as sprays and 

 as vapors. 



While there is no set rule or formula for making tobacco water or 

 decoction, one pound of stems is generally used to one gallon of 

 water. Warm water may be used, but never boiling, as the heat will 

 volatilize some of the nicotine and the essential ingredient of the 

 decoction would be lost. Tobacco water is sometimes mixed with 

 soap or other materials, but it is generally used alone, being cUluted 

 according to the hardiness of the plants on which it is to be applied. 



Chemically, tobacco is made up of many constituents, the most 

 poisonous being nicotine. The word nicotine or Nicotiana, the 

 genus to which tobacco belongs, was given to it in honor of John 

 Nicot, who, in 1560, sent seeds to the king of France, describing them 

 as the germs of a medicinal plant of great value. Different varieties 

 of tobacco and the locality where it is grown affect the quantity of 

 nicotine, plants grown on heavy moist soil possessing the highest 

 percentage of the principle. The .decoction varies in the amount of 

 nicotine present, having a range of from .53 to 5.21 per cent (Shaw), 

 depending not only upon the variety of the plant and locality in which 

 it is grown, but also upon the method used in obtaining the extract. 

 It is said that an addition of 10 per cent of lime to the water will more 

 efficiently draw the nicotine from the stems. 



Nicotine itself when pure is a colorless, volatile hquid which rapidly 

 changes to a brown color when exposed to the air. There are several 

 methods for extracting nicotine from tobacco. A relatively high 

 temperature cannot be used in extraction or the nicotine will be lost. 

 Some of the products now advertised are made from the pure nicotine 

 while others contain more or less of the other ingredients of the extract. 

 It is claimed by some that the nicotine is the principal active constit- 

 uent of a tobacco extract, while others hold that other ingredients 

 add to its effectiveness as an insecticide. 



