REPORT OF STATE ENTOMOLOGIST, 1898 229 



Icnown to be injurious. Aside from the additional handling and the 

 initial cost of the apparatus, the expense is but little. The value of the 

 chemicals used has been estimated by Professor Johnson at not over 2 

 , cents per 1000 nursery trees. The following formula is one commonly 

 recommended'^ : 



Fused cyanide of potassium, g8% pure i oz. by weight 



Commercial sulfuric acid i oz. by measure 



Water 3 oz. by measure 



The amounts given can be safely used on dormant nursery stock for 

 each 100 cubic feet of space, as reported by W. R. Gunnis, chairman of 

 the San Diego county board of horticultural commissioners (Howard, 

 Bull. 3, U. S. Dep't Agr., Div. Ent. 1898, p. 60). Prof. Johnson states 

 that repeated furiiigation will not injure nursery stock and that if necessary 

 the above amounts may be safely used to every 75 cubic feet of space. 



If no San Jose scale is present, the above quantities should be suffi- 

 cient for 150 cubic feet. Expose the stock to tlie action of the gas for 

 one hour. It will be found necessary to construct some form of a 

 receptacle in which to conduct the treatment. This may be simply a 

 tight box that can be inverted and its edges banked v\ith earth, or one 

 with covers, or even a building or portion of one, as circumstances may 

 dictate. It must be practically air tight, easily and quickly ventilated 

 and the stock should rest on a grating or other support that will permit 

 ready access of the fumes on all sides. The earth should be removed 

 from the roots of the stock so far as practicable before fumigation. The 

 gas should be generated as near the center of the lot to be treated as 

 possible and in case of large amounts, several gent-raiors should be 

 used and so placed that a rapid and uniform distribuiion of the gas will 

 be insured. The cyanide must be kept in tight bottles in a sate place, as 

 it is a volatile, deadly poison. The cubical contents of the fumigating 

 chamber should be estimated, the cyanide weighed out in amounts suffi- 

 cient for a treatment and put in paper bags. Pour the acid slowly into 

 the water, stirring the mixture constantly, otherwise drops may fly and 

 burn those in the vicinity. After the stock is properly arranged, pour the 

 necessary amount of dilute acid into a glazed earthen vessel, place the 

 cyanide while stiil in the paper bag into the acid and water, and close the 

 fumigator. The advantage of putting the cyanide into the acid and 

 water while still in the paper bag is that it prevents sputtering, which is 



aProf. W. G. Johnson, state entomologist of Maryland, as a result of a larg^e series of experi- 

 ments performed last year and the present season, recommends a sliL'htly different formula. He 

 advises the use of i ounce of cyanide of potassium, i^ ounces of the best jifrade of commercial 

 sulfuric acid and 2^ ounces of water to 113 cubic feet of space. In his experience, a more perfect 

 Teaction between the chemicals is obtained by modifying the formula as given above. 



