Important insecticides : directions for their preparation and use . deciduous fruits. This does not apply, however, to nursery stock,which may be brought together compactly and treated in mass in 127 32 fumigating rooms or houses. The general spread of the San Josescale in the East has made such fumigation of nursery stock, even^Yhen infestation is not shown or suspected, a necessary procedurebefore shipment or sale, to give the utmost assurance of safety to thppurchaser. Similarly this gas is the principal agency employed indisinfecting plant material coming from abroad, and will be the chief
Important insecticides : directions for their preparation and use . deciduous fruits. This does not apply, however, to nursery stock,which may be brought together compactly and treated in mass in 127 32 fumigating rooms or houses. The general spread of the San Josescale in the East has made such fumigation of nursery stock, even^Yhen infestation is not shown or suspected, a necessary procedurebefore shipment or sale, to give the utmost assurance of safety to thppurchaser. Similarly this gas is the principal agency employed indisinfecting plant material coming from abroad, and will be the chiefagency for such work wherever quarantine regulations prevail. Another very important use for hydrocyanic-acid gas is as a meansof controlling insect pests in greenhouses and cold frames. Theprocess is a special one, however, and entails considerable variation,owing to the wide range of plants to be considered. The details ofthe process are given in a special publication of the Bureau of Ento-mology (Circular No. 37), which will be supplied to anyone Fig. 6.—Tenting trees for gas treatment, San Diego, Cal. (Authors illustration.) A more recent use for this gas is in disinfecting houses of insectpests and vermin. The details of this treatment are given in Circular46, revised edition, of the Bureau of Entomology. In all work with hydrocyanic-acid gas, its extremely poisonous pm-ture must he constantly kept in mind and the greatest he taken to avoid inhaling it. FUMIGATION OF NURSERY STOCK. For the fumigation of nursery stock or imported plant materialin a dormant or semidormant condition, a building or room shouldbe provided, which can be closed practically air-tight, and it should befitted with means of ventilation above and at the side, operated fromwithout, so that the poisonous gas can be allowed to escape without 127 the necessity of anyone entering the chamber. The gas is generatedby combining potassium cyanide, sulpliuric acid, and water. Th
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