128 FUMIGATION METHODS 



cubic foot, and left until morning. The lice were all 

 destroyed, and there was no perceptible injury to the 

 plants. Indian corn, from ten to twelve inches high in 

 pots standing in one end of the house for experimental 

 purposes, was destroyed. 



Preparation of the house. The very poisonous 

 nature of the gas must be considered. The cautions 

 cited in Chapters III. and IV. should be heeded. The 

 house should be made as nearly tight as possible under 

 ordinary circumstances. The ventilators should be 

 arranged so several of them can be opened from the 

 outside. Plants that will not stand the stronger doses 

 of gas, if in pots, should be removed. The room 

 should not be fumigated immediately after the plants 

 have been sprinkled or watered. The floor of the 

 house should not be drenching wet, although it may 

 be damp. 



After estimating the cubic contents of the house, 

 and the amount of cyanide is determined, the quantity 

 needed can be figured out according to the directions 

 given in Chapter XIII. for nursery stock. Care 

 should be taken, however, to multiply the number of 

 cubic feet by the exact fraction of a gramme. For 

 instance, 0.25 gramme cyanide per cubic foot is used 

 for well-matured and dormant nursery stock, and 0.20 

 gramme for orchard trees out-doors; but no such doses 

 are used in greenhouses. Very good results have 

 been obtained where 0.15 gramme cyanide per cubic 

 foot has been used in greenhouses and cold frames for 

 the violet aphis. For other insects and plants the 

 amount of cyanide varies, as indicated above. 



