66 FUMIGATION 



Some plants can never be fumigated, or have never been suc- 

 cessfully fumigated. Roses, carnations, and chrysanthemums can 

 be successfully fumigated to kill aphids and white fly under proper 

 conditions. The plants may even be in full bloom. 



Plants should not be watered just before fumigation. In fact, 

 it would be well if the plants had not been watered for twenty- 

 four hours before the process. The temperature should be about 

 68 to 70 degrees, and the fumigation must be done at night; even 

 on a cloudy day it is apt to burn the foliage, while some entomolo- 

 gists seem to think it advisable not to fumigate on a bright moon- 

 light night. However, the moon does not seem to affect results. 

 The materials used in fumigation with cyanide are potassium 

 cyanide, sulfuric acid, and. water. The usual formula is: One 

 ounce potassium cyanide, two fluid ounces sulfuric acid, and three 

 fluid ounces water. Some prefer to use as much as six fluid ounces 

 of water to one ounce of sulfuric acid. The more water that is 

 used, the slower the gas is generated and the more evenly it is 

 probably distributed. The sulfuric acid is slowly added to the 

 water, which is contained in an earthenware jar, constantly stir- 

 ring. The earthenware jar is necessary, inasmuch as metal will 

 be acted upon by the sulfuric acid. The resulting mixture will be 

 hot, and the broken cyanide is added to it while still hot. 



The dose which is in general use is from one ounce to five ounces 

 of potassium cyanide per thousand cubic feet. It would be well 

 to first try the lighter dose, and if the insects are not killed and the 

 plants are uninjured, a stronger dose should be used. For overnight 

 fumigation use one-quarter to one-half ounce per thousand cubic 

 feet rather than a heavy charge for a short time. Under these con- 

 ditions there will be no danger in airing out the following morning. 



It would be well to advise the use of not more than one-quarter 

 of an ounce for the first dose to each thousand cubic feet for over- 

 night use, and not more than three ounces per thousand cubic 

 feet for fumigation for a half hour. If either of these doses is 

 used, and the insects are not killed while the plants show no injury, 

 the amount of cyanide per thousand cubic feet could be increased, 

 but not exceeding five or six ounces per thousand cubic feet as a 

 maximum quantity. 



Precautions. The gas is extremely poisonous, as is also the 

 case with the potassium cyanide. For that reason it is best not 

 to be in the house at the time that the cyanide is to be placed in 

 the jars. This can be arranged by putting the cyanide in bags 

 tied to a string suspended from the ceiling, end of the string to be 



