2 



BULLETIN 513, U. S. DEPAETMENT OF AGEICULTUEE. 



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 cat'eless 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 

 ,satisf actory 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. 

 This cover, which was de- 

 signed by Mr. E. 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 use'd with good 

 results, although to insure complete generation such a crock should 

 be tilted slightly in order that the cyanid may be covered. Crocks 



Fig. 1. — A cover device attached to a fumigation 

 generator. Corrugations in cover allow gas to 

 escape. (Woglum.) 



1 Bui. 79, Bur. Ent., U. S. Dept. Agr., p. 58, fig. 21, 1909. Bui. 90, Part I, Bur. Ent., 

 U. S. Dept. Agr., p. 75, flg. 12, 1911. 



