Materials and Formulas. 177 



destruction of plant lice, although other soft-bodied insects 

 may also be overcome by the applications. The mid-veins, 

 or "stems," are the parts sold for insecticidal purposes. The 

 simplest method of using them in greenhouses is to strew them 

 under the benches, making the layer two to four inches thick, 

 and renewing the stems eveiy five or six weeks. Tender plants 

 may easily be injured in this manner. Another common prac- 

 tice is to burn the stems in the houses, placing them in a sheet- 

 iron receptacle having the form of an enlarged stove-pipe placed 

 upon end, and having a perforated bottom. Legs should be 

 attached at the bottom to keep the fire from the floor. Paper 

 or shavings may be used for starting the fire, yet the stems 

 themselves should never come to a blaze, but only smolder, so 

 that large volumes of smoke may be produced. If the stems 

 are dampened, the operation is more effective. About one- 

 half pound of the stems to every 500 square feet of glass is the 

 quantity generally used. On account of the disagreeable smell 

 left in the house this remedy cannot always be employed. In 

 place of it there may be used semi-fluid extracts of tobacco 

 which are now upon the markets. When evaporated these are 

 very efficient in destroying aphis, and only a slight odor 

 remains. 



A decoction of tobacco stems is commonly employed. It 

 is prepared by steeping the stems in an amount of water 

 sufficient to cover them, and when their strength has been well 

 drawn out, the liquid is diluted so that it has the color of fairly 

 strong tea. It is then sprayed upon the plants, care being 

 taken that the insects to be destroyed are reached by the appli- 

 cations. This remedy can be used successfully where fumiga- 

 tion is not advisable, and it is cheap and effective. 



Powdered tobacco or snuff may also be used 'with success. 

 The plants to be treated should first be sprayed with clear 

 water, and then the powder may be blown on them. The water 

 causes it to adhere, and the decoction which probably results 

 acts energetically in destroying the pests. 



A tobacco decoction is frequently employed in place of pure 

 water in the preparation of other insecticides, and the presence 

 of the nicotine renders the preparation more efficient. With 

 kerosene emulsion, however, my experience has been such that 

 its use for this purpose cannot be advised. 

 N 



