Methods of Control 383 



gerous than the arsenicals. However, it loses its 

 insecticidal value by being exposed to the air. It 

 is a specific against slugs. 



(b) Contact Poisons. These are used most 

 extensively in the greenhouse. 



Water. Every florist appreciates this simple and 

 effective remedy. To be effective in dislodging and 

 destroying soft-bodied insects, it must be thrown 

 with considerable force on all parts of the plants. 

 For this purpose a good nozzle attachment is very 

 necessary. This simple remedy is effective in de- 

 stroying red spider, white flies, and mealy bugs. 



Tobacco, There are few substances which are 

 more extensively used than the many commercially 

 prepared tobacco products. Finely ground tobacco 

 is extensively used as an insecticide, especially for 

 Aphids. The product known as nicofumes is ex- 

 tensively used for indoor fumigation. 



Tobacco Decoction. This may be prepared by 

 boiling for one-half hour one pound of tobacco stems 

 in two gallons of water. It is then strained and 

 more water added to replace that which was lost by 

 evaporation during boiling. The liquid is used as 

 a spray against plant lice. 



"Black Leaf" and "Black Leaf 40." These are 

 two commercial products. The -latter is the more 

 concentrated of the two and is extensively used in 

 the control of sucking insects. The following table 

 by McCue * shows the dilutions that should be 



•McCue, C. A., Del. Agr. Expt Sta., Bui. 97: 17, 1912. 



