a” 
. 
ae 
2 BULLETIN 5138, U. S. DEPARTMENT OF AGRICULTURE. 
vailing impression that fumigation is a cumbersome procedure requir- 
ing considerable skill on the part of the operator. While it is true 
that much damage to the plants and injury to the operator may 
result from the careless use of hydrocyanic-acid gas, it is an estab- 
lished fact that this fumigant in competent hands is a safe, prac- 
tical, and economical means of controlling virtually all insect pests 
found in greenhouses. 
EQUIPMENT NECESSARY FOR FUMIGATION. 
GENERATORS. 
One-half gallon or one-gallon glazed earthenware jars serve as 
satisfactory generators, although it is preferable that the bottoms of 
the jars be rounded in- 
side, so that the cyanid will 
‘be covered with the acid 
and water, even with small 
doses, thus insuring the 
maximum generation of the 
gas. The number of gener- 
ators required is largely 
influenced by the size of 
the house or houses to be 
fumigated, and to avoid 
unnecessary delay in \case 
of breakage several extra 
crocks should be available. 
To insure uniform distri- 
bution of the gas it is ad- 
visable to employ gener- 
ators with covers, such as 
that illustrated in figure 1. 
Fic. 1.—A cover device attached to a fumigation This cover, which was de- 
Saber Says in cover allow gas to sioned by Mr. R. S. Wog- 
lum, is made of copper 
stamped in a concave form with corrugations to permit the escape 
of the gas. It is attached to the generator by hinges and held in place 
by a bolt which extends through the handle and can be raised by a 
slight pressure of the thumb as shown in the figure. If it is not 
possible to secure crocks of this description, those with straight sides 
which are not constricted inside at the bottom can be used with good 
results, although to insure complete generation such a crock should 
be tilted slightly in order that the cyanid may be covered. Crocks 
1 Bul. 79, Bur. Ent., U. S. Dept. Agr., p. 58, fig. 21, 1909. Bul. 90, Part I, Bur. Ent., 
UeoSmWept. Art. pe ca, oe. d2yeoina 
