448 



AN ECONOMIC ENTOMOLOGY. 



This mixture does not injure the trees or the foliage, and is 

 effective against young scales. It kills all that are moving about 

 in the larval condition, and also destroys recently fixed indi- 

 viduals; but it is ineffective against mature scales and the in- 

 sects under them. It acts by forming a thin varnish over the 

 scales, thus seaHng up and choking them. In the mealy-bugs 

 and cottony scales it mats up and seals the eggs so completely 

 that the larvse find themselves unable to emerge, A stronger 

 wash, used in winter, is made according to the following formula : 



Resin 30 pounds. 



Caustic soda (seventy per cent, strength) . . 9 pounds. 



Fish oil ^yi pints. 



Water sufficient to make 100 gallons. 



To make this mixture, boil all the ingredients together with 

 twenty gallons of water until thoroughly dissolved, adding hot 

 water from time to time, but not, after the boiHng begins, enough 

 to stop it. Three hours will be required for a complete mixture 

 of the materials, hot water to make fifty gallons being gradually 

 added and the mixture thoroughly stirred ; after this the balance 

 of one hundred gallons can be added in cold water. This is 

 really a soap varnish, deriving its effect from the caustic and 

 fish oil, while the resin forms an impenetrable covering. The 

 stronger mixture, or "winter wash," cannot be used in summer 

 without seriously injuring the foliage. 



Another wash frequently used on the Pacific coast, and found 

 very effective against the San Jose scale and other insects, is a 

 lime, salt, and sulphur mixture, made as follows : 



Unslaked lime 50 pounds. 



Sulphur 25 pounds. 



Stock salt 18 pounds. 



Water sufficient to make 100 gallons. 



This wash will do great damage to the trees if applied during 

 the growing season, and should be used only in winter. All the 

 sulphur and half the lime are placed in a kettle and twenty-five 

 gallons of water added, after which the contents of the kettle 

 are boiled briskly for an hour and a half, or until all the sulphur 

 is thoroughly dissolved. The solution, which at first is yellow 



