. 17 
Treatment consists in inclosing a tree (or nursery stock in greater 
or less quantities at once) with a tent and filling the latter with the 
poisonous fumes generated with potassium cyanide and sulphuric acid. 
For nursery stock, in place of a tent it is often more convenient and 
desirable to provide one or more fumigating boxes or small fumigating 
houses. 
The proportions of chemicals for growing plants are as follows: 
Refined potassium cyanide (98 per cent), 1 ounce; commercial sul- 
phuric acid, 1 fluid ounce; and 3 fluid ounces of water to every 150 
cubic feet of space inclosed. The generator may be any glazed earth- 
enware vessel of 1 or 2 gallons capacity, and is placed on the ground 
within the tent or on the floor of the fumigating chamber, and the water, 
acid, and cyanide, the latter in large lumps, added in the order named. 
























Fia. 1.—Tenting trees for gas treatment, San Diego, Cal. (author’s illustration). 
Treatment should continue forty minutes, and for growing plants should 
be practiced only on cloudy days or at night, the danger of injury to 
foliage or tender growth being much greater in sunlight. 
The table given below applies to citrus trees in southern California; 
in the winter treatment of nursery stock or deciduous orchards, a much 
greater strength can be employed if found necessary. 




: ; Diameter | = ype ph eat aoe eine Cyanide 
Meet). | through foliage (guid ounces). | {iusd ounces). | Potassium 
‘ , i 
6 24 14 14 
10 8 3 2 2 
12 10 6 3 3 
12 14 9 43 4} 
14 14 10 5 5 
16 16 12 54 5h 
18 16 | 12 6 6 
20 16 13 63 64 





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3019—No. 19 

