28 STATE BOARD OF AGRICULTURE. 



Hydrocyanic acid gas is largely employed on the Pacific coast in 

 clearing trees of scale insects, and it is very effective. In the East it 

 has been employed to any extent in Maryland only, but its usefulness 

 is limited, because of the cost of the necessary outfit. The expense 

 for materials is slight, but the tents and the labor required to move 

 them when the trees are of any size bring the price beyond the ability 

 of the average grower in New Jersey. In California, on large fruit 

 ranches, the outfit pays in the long run, and in many districts the 

 county owns the outfit and permits its use for a stated sum. In 

 Maryland the State has made comparatively large appropriations and 

 has given large powers to its entomologist. 



But while fumigation can hardly be recommended under present 

 circumstances for orchard work, it has a practical field in the nursery 

 and directions for its use there may be in place. Nursery stock may 

 be safely sumbitted to the hydrocyanic acid gas for hours and two 

 or three times during the dormant season. The essential point is a 

 tight house or box in which the stock is exposed to the fumes, and 

 this may be of any desired size or shape, depending upon the caprice 

 or necessity of the nurseryman. A house is better than a box and 

 should be first sheathed with fair matched or halved stuff, diagonally, 

 upright or otherwise, as desired. Then cover with a layer of building- 

 paper well lapped at the joints and weather-board in the usual way so 

 as to make an air-tight box. The roof may be iron, tin or tarred paper ; 

 only it must be as gas-tight as the sides. A shuttered window at one 

 end and large doors at the other should also be double and should 

 close tightly against felt or rubber strips. Both should be fitted 

 to lock from the outside in such a way as to clamp door and 

 shutter tightly in place. The bottom should be grated to 

 keep the stock from the earthen floor, and it goes without 

 saying that earth to cover the base should be banked against the 

 house from the outside, while inside the sill should be at least half 

 buried. In a small house a slide-box with a drawer reaching nearly 

 to the middle may open on the outside of the house, and in this the 

 jar with chemicals may be loaded, shoved into place when the house 

 is closed, and the opening protected in any desired way while fumi- 

 gation is going on. In a large house one or more jars may be placed 

 near the middle in a protected space and the cyanide may be dropped 

 in when all is ready to close doors immediately. 



For nursery stock the formula for every hundred cubic feet of 

 space is : 



Cyanide of potassium, 98% pure, 1 oz. by weight. 



Sulphuric acid, sp. g. 1.83 \y 2 oz. by measure. 



Water 2% oz. by measure. 



