oiieratoi- to iutrortnce the cyankle to the diUitea sulphiirie acid through a 

 wiiulow. the cyanide being placed at the end of a long stick or rod, or lieing 

 lowered into the acid by a string and pidley. The window must be closed 

 immediately after the addition of the cyanide, so that the operator may escape 

 the fumes. Strawson recommends the pouring of the diluted acid from a 

 bottle fitted with a cork in which two slits are cut, one to let in air and the 

 other to allow a small and even stream to flow upon the cyanide, the object 

 lieiug to provide a slow and even disengagement of gas. The bottle should be 

 arranged so that it can be tilted up when all is ready. 



It is of importance also that the hydrocyanic acid gas fumes be distributed 

 over the house, and this may be done by an arrangement of fans which can 

 be worked from the outside. 



Fumigation should take place in the evening, or aft(>r nightfall, and niit in 

 strong sunlight. The temperature of the house should be from 50° to 60° F. 

 The plants to be treated should be dry. The surface of the soil of the house 

 should also be as dry as practicable. Experiment has shown that the eggs of 

 the woolly aphis may remain unaffected, and therefore fumigation should be 

 repeated in ten days. Eggs of the apple mussel scale are also unaffected by 

 gas of the .strength mentioned. 



Points to he Currfiillii yotcd. — The work should be done by a careful and 

 skilled operator, for the cyanide and its fumes are very poisonous and danger- 

 ous to human and animal life. 



The treated room or conservatory must be kept closed during fumigation 

 from three-quarters of an hour to an hour, after which the room should be 

 ventilated, the windows, etc., being opened from the outside, and no one should 

 enter until an hour has elapsed. While opening the windows, etc.. the operator 

 should be careful not to enhale the escaping fumes. 



It is safer not to fumigate when the plants are in bloom. 



yiirscni Stocli. — In the treatment of nursery stock the Inishes or young 

 trees should be placed in an air-tight box or canvas tent of known capacity, 

 and subjected to the fumes of hydrocyanide gas for one hour. Large numbers 

 can be treated at once at little expense. 



When the time has expired the tent or box should be opened in such a 

 way that the wind blows the fumes away from the operator, and should be left 

 to ventilate for half an hour before the stock is removed. 



Trees in the orchard may also be treated by the use of a canvas tent or 

 cover. 



C.\Nv.\s Covers for Ftmig.^tixo. 



The practice of using canvas covers for fumigating is not so common in 

 Great Britain as in some other countries and the method followed in the 

 Colonies may here be given for the guidance of those who wish to undertake 

 orchard fumigation with h.vdroc.vauide acid gas. According to Claude Fuller, 

 the Xatal Government Entomologist, the covers should be of a light, durable 

 material, and comiiaratively gas-tight, the most suitable, probably, being 

 canvas. Eight-ounce American duck canvas is recommended. 



There are three tjiies of covers — sheets, tents, and box covers. The sheets 

 are octagonal in form, and can be further enlarged by sewing on a " .skirt "' 

 round the edge. These can be easily lifted over small trees up to six or seven 



