FUMIGATION OF NURSERY STOCK.* 
S. A. BracuH. 
INTRODUCTION. 
The best known way of killing San José scale on dormant nurs- 
ery stock is by fumigation with hydrocyanic acid gas. This 
treatment is valuable not only against San José scale but against 
all scale insects which do not winter in the egg stage. It will 
doubtless also check the spread of some other kinds of injurious 
insects which are liable to be distributed on nursery stock. 
Plain directions for fumigating Gormant nursery stock with 
hydrocyanic acid gas will first be given, after which suggestions 
will be made as to the location and construction of fumigation 
houses or chambers. 
APPARATUS, MATERIALS AND METHOD. 
| THE EQUIPMENT. 
The things needed for fumigating nursery stock with hydro- 
cyanic acid gas are: (1) The chemicals; (2) a suitable dish in 
which to mix them; and (3) an air-tight box or chamber to hold 
the stock while it is being fumigated. 
CAREFUL WORKMEN NEEDED. 
It is not hard to kill the San José scale; the difficulty is to kill 
it without injuring the plant upon which it is living. The scale 
insect is fastened immovably to the plant with its mouth parts 
stuck into the bark ‘so that it may suck the plant juices which 
constitute its food. It cannot be given poison in its food, but 
must be killed by something which comes in contact with its 

*Reprint of Bulletin No. 174. 
This substance is commonly known in liquid form by the name “‘prussic 
acid.” 
