4 CIRCULAR 457, U. S. DEPT. OF AGRICULTURE 



should be sterilized b/7 heating. In caves, owing to poor ventilation 

 and ground beds, and in cellars, owing to the possibility of the gas 

 escaping, it is not always possible to do this. Formaldehyde is a 

 good germicide and fungicide, but the gas from burning sulphur is 

 about as good, and is also a useful insecticide, and is specific for 

 mites. Before the house or room is fumigated or sterilized it should 

 be made as airtight as possible by tightly closing all ventilators and 

 other openings and by pasting paper or plastering mud over all 

 cracks. 



In cellars and other places close to dwellings it is not advisable to 

 use sulphur or other materials as fumigants, unless such places can 

 be sealed tightly enough to prevent all fumes from escaping. Sulphur 

 should not be used where there is any possibility of the fumes reach- 

 ing mushroom beds in production, as the growing mushrooms will 

 be damaged. 



FORMALDEHYDE FUMIGATION 



Formaldehyde is used at the rate of 1 quart to 1,000 cubic feet of 

 the air space to be fumigated. One pound of permanganate of 

 potash is used to the quart of formaldehyde. Crocks, wooden buck- 

 ets, or other containers of about 10-gallon capacity are needed, each 

 of which will take care of 1 gallon of formaldehyde. Four pounds 

 of the permanganate is placed in each of these, and a gallon of the 

 formaldehyde in a wide-mouthed container beside it. Starting at 

 the end of the house farthest from the door, the operator pours the 

 formaldehyde into the containers with the permanganate as he moves 

 toward the door, and leaves the house or room at once, closing and 

 sealing it. The reverse of this precedure, dropping the permanga- 

 nate into the containers containing the formaldehyde, is sometimes 

 the easiest method. 



SULPHUR FUMIGATION 



In sulphur fumigation, a good grade of flowers of sulphur should 

 be used at the rate of 5 or 6 pounds per 1,000 cubic feet of air space to 

 be fumigated. It is most commonly burned in pans or metal trays 

 with the edges high enough to prevent the molten sulphur from flow- 

 ing over the edge and setting fire to the house, or in oil drums cut in 

 half lengthwise. A little excelsior or crumpled paper is placed along 

 the bottom of four or five pans, and the sulphur is poured along each 

 side of it. Some growers prefer to use less sulphur per pan, covering 

 the bottom of each tray with an inch layer of excelsior and sifting 

 the sulphur over this. Still another method is to put excelsior in the 

 bottom of the container and over this to place a piece of coarse screen, 

 cover the screen with a piece of newspaper, and pour the sulphur 

 upon this. The use of a larger pan containing water, into which the 

 smaller one containing the sulphur is placed, is an effective aid in 

 preventing fire and accidents. In the case of houses having dirt 

 floors, pits may be dug therein and the sulphur burned as in the pans. 

 Sulphur should not be burned upon concrete floors, as the heat is likely 

 to cause the concrete to crack and buckle, thus throioing the burning 

 sulphur about and setting flre to the house. 



In any method the important thing is to get as complete combus- 

 tion in as short a time as possible. Recent experiments have shown 

 that it is very unusual to get complete combustion by any method of 



