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NEW YORK STATE MUSEUM 



fumigation with hydrocyanic acid gas. This treatment should be given 

 in the winter time when the trees are dormant and is of particular value 

 where a large number of small trees must be treated. The tents necessary 

 for fumigation are too expensive for moderate or large size trees. The proc- 

 ess consists in covering the tree with a canvas tent and generating the gas 

 underneath it by applying diluted sulfuric acid to potassium cyanid. This 

 method is extensively used in California on citrus trees and has been 

 employed to some extent in the east. There are a number of different 

 tents which have been designed for this purpose by various investigators, 

 and those wishing to treat their trees may find it advantageous to consult 

 Professor Johnson's Funiii^ation Methods.^ Those who have only a few 

 trees and wish to employ the gas in a small way may find the following 

 directions of service. The trees should be exposed to the action of the gas 

 for 35 minutes at least, and one ounce of the cyanid (gS'J purity) should be 

 used to every 75 cubic feet of space together with an equal amount, by 

 liquid measure, of the best commercial sulfuric acid (specific gravity 1.83) 

 aud three times that amount of water. Professor Johnson has advised using 

 13^ ounces of acid to 2 '/j^ ounces of water to each ounce of cyanid. The 

 cyanid should be placed in an earthenware crock near the trunk of the tree, 

 as distant as possible from the tent, and when everything has been prepared, 

 the diluted acid (which is prepared by turning the acid slowly into the water, 

 stirring constantly in the meantime) should be emptied into the crock con- 

 taining the necessary amount of cyanid and the tent quickly made tight all 

 around. These materials are extremely dangerous to handle, the acid will 

 burn almost anything and causes very bad sores, while the cyanid is one of 

 the most deadly poisons known. The fumigated trees should be covered 

 with a tight tent which is usually made of 8 ounce cotton ducking thor- 

 oughly coated with boiled linseed oil, paint or other material in order to 

 make it gas tight. The tent may be bell-shaped or rectangular and sup- 

 ported by a frame or may even consist of a large sheet thrown over the 

 tree. The form supported by the frame is the better because of the ease 

 'Orange Judd Co. 1902. 



