New York Agricultural Experiment Station. 337 



; the fumigation. i 



When the stock has been put into the fumigation chamber, 

 place a glazed earthen-ware dish having a capacity of a gallon 

 at least on the floor near the middle of the room. If the room 

 is large use one large gas generator iu each 1000 cubic feet of 

 space, or use several smaller ones properly distributed. 



To generate the gus, first pour into the dish the required 

 amount of * water, then add the sulphuric acid. This process 

 should not be reversed because when the water is poured into 

 the acid a more violent action takes place and the acid is liable 

 to be spattered upon the person doing the work. Lastly drop 

 into the dish the paper containing the potassium cyanide. Get 

 out of the room and close the door as quickly as possible ftewgr 

 very careful not to get a breath of tlie gas. From the time fumi- 

 gation begins till the room has been thoroughly ventilated a 

 DANGER placard should be displayed at the door. 



Time. — The entomologists who have investigated this subject 

 are not yet agreed as to the length of time" which should be recom- 

 mended for the fumigation of dormant nursery stock but they 

 generally give from 30 to 50 minutes. Sirrine advises that, 

 when using the formula given below, the stock be fumigated for 

 one hour. In Johnson's tests, well matured stock of apple, plum, 

 etc., stood treatment one hour with gas at a strength far above 

 the standard used ; so that in general with the standard strength, 

 no damage need be feared from an overdose with well-matured 

 stock.* It is well to be on the safe side and continue the fumi- 

 gation long enough to secure the full benefit of the operation. 



Yentilation. — After the stock has been fumigated the room 

 must be ventilated for at least ten minutes before entering it. 

 This rule must be strictly enforced because anyone who' enters 

 •the room before it has been properly ventilated endangers his life. 



"Johnson, W. G. Some physiological effects of hydrocyanic acid gas 

 upon plants. Sci. Amer. Sup,, 48 : 20026. 



22 ~: 



