34 INSECTS NOXIOUS TO AGRICULTURE. 



to be one of the best remedies against the larvae 

 and adult insects proportions from ilb. to Jib. soap 

 to one gallon of water (Comstock ; Hubbard ; Personal 

 experiment) . 



15. Soda, caustic. Strongly recommended by many persons. 



It injures the tree, and does not kill the eggs two 

 things which are decidedly against its use. Gar- 

 deners may have been led to employ it from finding 

 that in some instances it clears away the black 

 fungus-growths (Chap. III.), and imagining this to be 

 a clearance also of the scales. 



16. Soda, silicate. Kills some insects, but no eggs, and in- 



jures the tree (Hubbard). 



17. Sulphate of iron. "A common ingredient in patent 



remedies;" most injurious to vegetation. It does not 

 affect scale-insects (Hubbard) . 



18. Sulphur. Another substance, the object of a kind of 



superstitious veneration amongst gardeners. It is 

 excellent against fungoid growth, but of little value 

 against scale-insects. Here, again,, the clearing of the 

 black fungus has probably been taken to mean also the 

 destruction of the insects (Hubbard ; Comstock ; Per- 

 sonal experiment). Comstock says that in America 

 people often bore holes in their trees and stuff them 

 with sulphur, under the notion that the substance 

 will be taken up by the sap, and poison the insects : 

 quite a futile idea. 



19. Sulphur and lime. A dangerous compound, and useless 



unless applied in such strength as to kill the tree. 

 Its fumes are poisonous, and it may seriously injure 

 the face and hands (Hubbard). 



20. Sulphur and snuff. Equal parts mixed and dusted over 



Lecanium hesperidum on a wet day were quite suc- 

 cessful (Comstock). But the mixture would be too 

 expensive except for conservatory plants, and doubt- 

 less the snuff alone would be quite as efficacious. 



21. Sulphuric acid. " Killed nearly all the scale-insects, 



and very nearly killed the tree" (Hubbard). No 

 mention is made of its action on the eggs. 



22. Soot. Useless (Hubbard ; Comstock ; Personal experi- 



ment) . 



