SOME MUSHROOM DISEASES AND THEEEt CARRIERS 5 



Fumigation by the chlorate method consists of mixing commercial 

 40 per cent formaldehyde solution with sodium chlorate and boiling- 

 water, the heat of the reaction acting to volatilize formaldehyde. 

 The following materials are required : Formalin ; sodium or potas- 

 sium chlorate; boiling water; bags, paper or cloth, of convenient 

 sizes; receptacles, which should be of uniform size, deep enough so 

 that the formalin will not boil over when the chlorate is added ; they 

 may be half barrels, washtubs. or iron or earthenware vessels, but 

 they should not be of glass, as the heat evolved may break them. 

 Ordinary galvanized pails are quite satisfactory and may be placed 

 in pans, similar to dish pans, very wide so as to serve as trays for 

 the formalin receptacles. Allow 1 pound of formalin for every 

 1,000 cubic feet of space and 5 ounces of sodium or potassium chlorate 

 to every pound of formalin. If the house is of the usual size (24 

 by 100 feet), use at least three receptacles for generating the gas. 



Weigh out the proper quantity of chlorate, divide it into as many 

 parts as the number of vessels used, and put it into paper or cloth 

 bags. Measure the proper quantity of formalin and divide it equally 

 among the vessels. Place the vessels, each standing in a large flat 

 pan, in their proper places in the building. The formalin should 

 not be left standing uncovered very long in the house, as consid- 

 erable discomfort may be experienced by the workers. 



In houses of average size place the vessels in the center aisle. In 

 larger houses one or more vessels should be placed in each aisle, as the 

 gas must be evenly distributed to be effective. 



Place a bag of chlorate beside each vessel. When everything is 

 ready, beginning at the end of the aisle farthest from the door, place 

 the chlorate in the formalin, and pour boiling water into the pan 

 containing the vessel. Go quickly to the next vessel and repeat. 

 After the chlorate has been added to each vessel, close the door at 

 the end of the aisle and seal it with paper as quickly as practicable, 

 as the action of the chemicals is rapid. It must be remembered that 

 where there is one person to each aisle, the work of dropping the 

 bags of chlorate into the formalin must be done at the same time, in 

 order that all of the persons may get out at the same time and before 

 the gas has become strong. 



Keep the house closed for at least 24 hours. If possible do not open 

 until just before the new beds are to be installed, thus preventing any 

 chance of their being infected after fumigation. If the spent com- 

 post was piled near the house after its removal, under no circum- 

 stances open the house until this has been removed from the vicinity 

 and the ground where it was placed thoroughly disinfected in the 

 manner before described. 



Approximately 1 pound of formalin per 1,000 cubic feet of air 

 space is required for the boiling formalin method. In this method 

 a tank containing the formalin is placed over a stove or a fire out- 

 side of the mushroom house. Pipes conduct the vaporized formalin 

 into the mushroom house. This method is extremely cheap and 

 highly effective. 



The potassium permanganate method was advised by the depart- 

 ment in the early studies of the disease, but the price of potassium 

 permanganate became very high during the World War, and the sub- 

 stitute methods above mentioned have been found satisfactory and 

 less expensive. 



