1 June, 1898.] QUEENSLAND AGRICULTURAL JOURNAL. 505 
A suitable arrangement for fumigating nursery stock is a gas-tight box of 
‘convenient size, made of tongue-and-groove wood put together with white lead, 
with the door or cover closing against list or felt. and capable of being clamped 
into place, one corner being partly boarded off to hold the earthenware jar, 
and above it a ring that connects with a slender rod leading to the outside 
to serve the means for inverting the cup (in which the cyanide may be placed) 
that is fixed into it. The box may be rendered to a further extent tight by 
the use of grafting wax. 
For the accomplishment of the same work the following method may also 
be employed :—Pieees of wood of equal length are set up at the four corners 
of an oblong piece of ground and united above by four horizontal bars. The 
ground is surrounded by a shallow trench containing loose earth. The plants 
being placed within the enclosure, the whole is now covered with a sheet of duck 
(8 oz.) or drill already rendered gastight with boiled linseed oil; and of such 
dimensions that its edges dip well into the dite and turn up. These are now 
well covered with the loose earth of the ditch, and one corner of the sheet 
raised and quickly lowered again to add the cyanide of potassium to the acid 
and water in a previously introduced earthenware vessel. 
All trees dealt with in this manner should be in a dormant condition, and 
it is, moreover, desirable that the unprotected roots be not exposed to the 
direct action of the gas of thé strength indicated. Nursery stock is therefore 
best treated after being previously closely heeled in. i 
hme) 
In using hydrocyanie acid gas it must be borne iu mind that both it and 
the cyanide from which it is derived are violent poisons. ‘The latter, therefore, 
when not in use, should be kept under lock and key, and care taken not to 
breathe the gas itself. It should not be generated, moreover, until the box in 
which it is to be evolved be closed; and special precautions should also be 
taken in opening the latter when the process is complete and in ulowing it to 
escape. Moreover, operations involving its use should, if practicable, be 
conducted in the open air or in an open shed. 
If the Pernicious Seale already occurs in the garden or orchard and only 
a small proportion of the total number of trees that it contains are infested, it 
will be generally expedient to cut these down, and burn them if possible 
without removal. Big old trees and neglected or abandoned ones harbouring 
the insect should be similarly dealt with; for in the first instance the risk of 
avoiding further dissemination should be opposed, even though such action as 
is recommended involve considerable sacrifice ; ridding big old trees of scale 
is a costly work ; and public nuisances should be abated. 
The treatment of Pernicious Scale-infested trees that it is decided shall 
not be destroyed is a matter of considerable difficulty. When the insect is 
especially vulnerable—thatis, when it occurs as an active unprotected larva—the 
employment of direct treatment (other than that which consists in the use of 
hydrocyanic acid gas) is not liable to be attended by any certain result, unless 
‘repeatedly resorted to—a procedure that is not economically justifiable. ‘This 
is because the young do not issue from the parent scale together, but continue 
to emerge during many successive days (vid. p. 498), so that an application 
that is fatal to the early born young of any individual does not come into 
contaet with those that shortly succeed them. And, moreover, when the young 
are about—z.e., during the summer months—washes that will kill them, and at 
the same time penetrate and so destroy the parent scales as well, cannot be 
safely employed since they require to be of such caustic strength as will injure 
the trees themselves also. Accordingly, measures must be directed towards 
’ the mature inseets, and sufficiently concentrated washes employed to accomplish 
their destruction, and winter treatment, when the buds are dormant, must be 
therefore largely depended upon for the accomplishment of really safe and 
successful work. . 
