32 
fumigating rooms or houses. The general spread of the San Jose 
scale in the East has made such fumigation of nursery stock, even 
when infestation is not shown or suspected, a necessary procedure 
before shipment or sale, to give the utmost assurance of safety to the 
purchaser. Similarly this gas is the principal agency employed in 
disinfecting plant material coming from abroad, and will be the chief 
agency for such work wherever quarantine regulations prevail. 
Another very important use for hydrocyanic-acid gas is as a means 
of controlling insect pests in greenhouses and cold frames. The 
process is a special one, however, and entails considerable variation, 
owing to the wide range of plants to be considered. The details of 
the process are given in a special publication of the Bureau of Ento- 
mology (Circular No. 37), which will be supplied to anyone inter- 
ested. 
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Fic. 6.—Tenting trees for gas treatment, San Diego, Cal. (Author’s illustration.) 
A more recent use for this gas is in disinfecting houses of insect 
pests and vermin. The details of this treatment are given in Circular 
46, revised edition, of the Bureau of Entomology. 
In all work with hydrocyanic-acid gas, its extremely poisonous na- 
ture must be constantly kept in mind and the greatest precautions 
must be taken to avoid inhaling tt. 
FUMIGATION OF NURSERY STOCK. 
For the fumigation of nursery stock or imported plant material 
in a dormant or semidormant condition, a building or room should 
be provided, which can be closed practically air-tight, and it should be 
fitted with means of ventilation above and at the side, operated from 
without, so that the poisonous gas can be allowed to escape without 
127 


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