262 MONTANA EXPERIMENT STATION. 



dissolved. For this reason the following formula is considered 

 much more reliable : 



White arsenic 2 pounds. 



Sal soda 4 pounds. 



Water 2 gallons. 



Boil for about fifteen minutes or until all is dissolved, leaving 

 a clear liquid. Add water enough to replace what has boiled away 

 to prevent chrystalization of the arsenite of soda. A large quantity 

 may be prepared at one time and kept as a stock solution to be used 

 when desired. It should be covered to prevent evaporation and 

 plainly labeled for it is a deadly poison. One pint of this stock 

 is approximately equivalent to four ounces of Paris green. It should 

 be used only in a solution in which lime is present for, as seen above, 

 it is soluble in water. With lime it forms arsenate of lime which is 

 the resulting product of the previous formula. It may also be used 

 in connection with Bordeaux mixture, in which case Bordeaux mix- 

 ture is used as a diluent in place of water. 



Counting the cost of the preparation of arsenite of lime it is not 

 probable it will be found cheaper unless large quantities are to be 

 used. In using this substance in preference to Paris green, however, 

 one avoids the danger of purchasing adulterated goods. 



Hellebore. 



Hellebore has a narrow range of usefulness and is efifective 

 chiefiy against saw-fly larvae. It kills by coming in contact with 

 soft-bodied insects or by being eaten. It is usually dusted on the 

 foliage either pure or mixed with twice its amount of lime, plaster 

 or cheap flour. The foliage should be moist when it is applied in a 

 dry form, otherwise it will not adhere. In Montana where the foli- 

 age is almost perpetually dry, it would be better to apply it as a 

 spray at the rate of one ounce to 2-4 quarts of water. Hellebore is 

 not poisonous to man. 



Kerosene Emulsion. 



Pure kerosene is fatal to almost all insects. It is extremely pen- 

 etrating and enters the breathing pores of the insects and interfering 

 with their breathing causes their death. Pure kerosene, however, 

 is more or less injurious to plant life and for this reason has to be 

 diluted in some way. Since it will not mix with water it is necessary 

 to form an emulsion, and soap is usually used for this purpose. 

 A good formula is : 



Ordinary bar soap ^ pound. 



Soft water i gallon. 



Kerosene 2 gallons. , 



