CYANIDE FUMIGATIOX OF MUSHROOM HOUSES Q 



doubled paper bags are used for the cyanide, or if the operator moves 

 rapidly, he is usually completely out of the house before the first 

 generator commences to evolve gas. For greenhouse fumigation 

 there has been used a. rod with arms that permits the cyanide to be 

 dumped into all generators simultaneously from outside the house. 

 This would be inexpensive and its use would remove all hazard. Reg- 

 ulation of the dosage is very easy with sodium cyanide. In this 

 connection, although the concentration secured with the dosage of one- 

 half pound per 1,000 cubic feet of air space, or 8 pounds to the stand- 

 ard house of 16,000 cubic feet, seems high enough for the average 

 house, an increase to 10 ounces per 1,000 cubic feet (or 10 pounds per 

 standard house) would seem advisable, in order to give a generous 

 margin of effectiveness. 



From the standpoint of cost, calcium cyanide at the standard 

 dosage of 1 pound per 1,000 cubic feet of air space and liquid hydro- 

 cyanic acid at the equivalent dosage come to the same figure ($4 at 

 the present time) per house. Use of an equivalent dosage of sodium 

 cyanide would bring down the total cost to a little less than half 

 that figure ($1.98 at the present time) . 



SUMMARY AND CONCLUSIONS 



In the fumigation of commercial mushroom houses, it was shown 

 that when chemically equivalent dosages of calcium cyanide, sodium 

 cyanide with acid (1-1^-2), and liquid hydrocyanic acid (1 pound 

 calcium cyanide, one-half pound sodium cyanide and one-quarter 

 pound hydrocyanic acid per 1,000 cubic feet of air space) were used, 

 the last two were much superior to calcium cyanide in the concentra- 

 tion of gas obtained. 



Liquid hydrocyanic acid gave a slightly higher maximum concen- 

 tration of gas than sodium cyanide and acid. From the standpoint 

 of safety, if properly handled, there is little choice between the two. 



The average results from tests made in a fumigating chamber 

 show that mushroom insects and mites in a temperature brought from 

 75° or 80° to 100° F. in from 6 to 8 hours, held at 100° for from 7 to 

 9 hours, and then fumigated with hydrocyanic acid gas, were all 

 killed by a concentration that reached a maximum of 3.6 mg per liter, 

 had a mean of 1.67 mg per liter, and required 44 minutes to drop to 

 0.4 mg per liter. An average of the curves drawn from single fumiga- 

 tions made in the fumigation chamber which produced slightly under 

 100 percent kill shows a maximum concentration of 2.9 and a mean 

 concentration of 1.56 mg per liter, with a drop to 0.4 mg per liter in 

 38y 2 minutes. 



Multiple or " interval " fumigations were found to be less effective 

 than those in which the same total amount of material was used in 

 one dosage, giving a higher maximum concentration but a shorter 

 exposure. 



The cost of fumigation per unit with sodium cyanide is about one- 

 half that with either of the other two materials. It is recommended 

 that on account of the leakage encountered in many of the houses the 

 dosage for the average mushroom house be increased to 10 ounces of 

 sodium cyanide or to 5 ounces of the liquid hydrocyanic acid per 1,000 

 cubic feet of air space. 



