140 SPRAY MACHINERY AND SPRAY MATERIALS 



than to dilute it with water. The commercial solutions are 

 thoroughly reliable. They are fairly well standardized now 

 and the standard liquid test is about 33 degrees on the 

 Baume hydrometer, which is the density of the solution. 

 These solutions when used as insecticides must be diluted 

 and sprayed on the plants when they are in a dormant state. 

 When the solution tests 33 degrees Baume, one gallon of 

 the mixture should be diluted with 7 or 8 gallons of water. 

 Solutions less dense should be diluted as follows: 



TABLE OF DILUTIONS FOR THE DORMANT SPRAY. 



Satisfactory insecticides for soft-bodied insects can be 

 made from soap. Fish-oil soap is probably the best, although 

 common laundry soap is very good. The solution is made by 

 cutting up one pound of soap into small pieces and dissolving 

 it by boiling in 4 or 5 gallons of water. This is a good spray 

 for plant lice. 



NICOTINE PRODUCTS. 



The nicotine products are perhaps the most satisfactory 

 contact insecticides we have for the plant lice. The active 

 principle in these solutions is nicotine sulphate. Some com- 

 mercial products, namely, the Black Leaf 40 and the Nico- 



