INJURIOUS INSECTS OF 1903. 109 



eign oils, the former having a paraffin and the latter an 

 asphalt base. The true indication of the safety of petro- 

 leum as an insecticide evidently depends upon its specific 

 gravity; as it has been found that petroleum having a 

 specific gravity of 43 degrees or above (Baume oil scale 

 at a temperature of 60 degrees F.) is less likely to injure 

 the trees than petroleum of a lower specific gravity, al- 

 though oils of a lower specific gravity have been success- 

 fully used in some instances, notably in Canada." (N. Y. 

 State Bui. 202. 1901.) 



This is one of the best scale insect remedies. It should 

 be applied on a bright, sunny day in early spring, and 

 must be applied thoroughly, evenly and avoid over- 

 drenching. 



On perfectly dormant apple trees a 40 per cent emul- 

 sion is used ; on perfectly dormant plum trees a 25 per 

 cent emulsion is used. 



22. Cupram — (Ammoniacal Copper Carbonate.) 



23. Formalin — 



This has been found to be the best remedy for potato 

 scab and smuts. 



For Potato Scab — Soak the seeded potatoes for two 

 hours in a solution of a ^^-pint of formalin to 15 gallons 

 of water. 



For Grain Smuts — Soak the seed one to two hours in 

 a solution of i pound of formalin to 50 gallons of water. 



24. Gasoline — 



This is used like benzine for bedbugs by spraying into 

 crevices, etc. 



25. Green Arsenoid— (See Scheele Green.) 



This insecticide is applied in the same manner as Paris 

 Green. It contains no acetic acid, and is thus not so liable 

 to burn the foliage. It costs less than Paris Green (12c. 

 to 15c per pound), and being finer remains in suspension 

 longer. Dr. Marlatt, of the Division of Entomology, U. 

 S. Department of Agriculture, says it should replace Paris 

 Green as an insecticide. (Colorado Bui. yi, 1901.) 



