REPORT OF STATE ENTOMOLOGIST, 1898 229 
known 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 1ooo nursery trees. The following formula is one commonly 
recommended ¢: 
Fused cyanide of potassium, 98% pure...........--- 1 oz. by weight 
Commercial sulfuric acid essay oc 2 et tales op eve eae 1 oz. by measure 
IWEeitcreeat metre aay. 2) ate eat eis. sear She eey npn ee ica ater ate ae 3 oz. by measure 
The amounts given can be safely used on dormant nursery stock for 
each roo 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 fumigation 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 José scale is present, the above quantities should be suffi- 
cient for 150 cubic feet. Expose the stock to the 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 with 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 generators should be 
used and so placed that a rapid and uniform distribution of the gas will 
be insured. The cyanide must be kept in tight bottles in a safe 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 still 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 large series of experi- 
ments performed last year and the present season, recommends a slightly different formula. He 
advises the use of x ounce of cyanide of potassium, 1} ounces of the best grade of commercial 
sulfuric acid and 24 ounces of water to 113 cubic feet of space. Inhis experience, a more perfect 
reaction between the chemicals is obtained by modifying the formula as given above. 
‘ 
