274. QUEENSLAND AGRICULTURAL JOURNAL. [1 Aprin, 1899. 
destruction of the Red Scale of the orange (Aspidiotus Aurantii), the Purple 
or Mussel Scale (Mytilaspis citricola or M. fulva), and all other armoured 
scales. In Cape Colony it is now being largely used for the destruction of 
the Red Scale, and Mr. Charles P, Lounsbury, the Government Entomologist, 
states that it is the cheapest and most effectual remedy for this particular 
insect. The use of hydrocyanic acid in these colonies is even of more recent 
introduction, as up till some fifteen months ago, when this Department com- 
menced experimenting, I am only aware of its haying been tried by three 
persons—viz., Mr. G. Quinn, Inspector of Fruit, South Australia, and Messrs. 
A. Philp, junr., Gatton, and O’Brien, Sunnybank, in this colony. 
Messrs. Philp and O’Brien only carried out experiments in a small way, 
though as far back as 21st December, 1896, Mr. Philp wrote to this Depart- 
ment that the scale (White), for which he was treating his orange-trees, 
“seems to be perfectly dry and without life’’; and also “orange bugs of 
various kinds were found dead under the tree after the tarpaulin was removed.” 
Mr. Quinn gave his experience of this method of treatment at the Inter- 
colonial Conference of Fruitgrowers held in Brisbane during June, 1897, and 
stated: “During the past year he had made several experiments for the 
treatment of the Red Scale, and at the present time (June, 1897), for one 
living scale to be found on the trees treated with eyanide, thirty will be found 
on those treated with the resin wash and fifty on those treated with kerosene 
emulsion. He had tried the cyanide process on other trees in other orchards, 
and in one case, as a result, not a single living insect could be found, although 
neighbouring trees were affected. The fruit which had been produced this 
season from ‘cyanided’ trees was particularly clean, and the trees themselves 
were looking clean and healthy.” 
The experiments conducted by this Department have ‘been varied and 
extensive, and have been carried out on various kinds of fruit and ornamental 
trees that have been affected witir many varieties of scale insects, including 
the following :—Red Scale of citrus fruits, Circular Black Seale, Mussel 
Scale, White Scale, Glover Scale, Greedy Scale, various species of Lecaniums, 
San José Scale, and Pink Wax Scale; and in every case, the insects treated have 
been destroyed. Considerable difficulty was encountered in several ways 
during the course of the experiments, the chief of which was to obtain suitable 
material for the sheets and bell tents, as we found that the material and dressing 
recommended by the Californian authorities was unreliable and unsuitable, and 
several other materials tried were not a success. Oiling the sheets and tents 
is a mistake, as, though it renders them absolutely gas-tight, it, at the same 
time, injures the texture of the fabric, rendering it rotten and easily torn, 
Acting on the advice of Mr. Lounsbury, who has had a similar experience, we 
are using the best Canadian duck, without oiling, and find that 1 stands much 
more work, and is sufficiently gas-tight for all practical purposes. In order to 
preserve the material, we have tanned the sheets and tents made of Canadian 
duck with a strong extract of ironbark and wattle-bark, but have used no 
material to render it gas-tight. 
Considerable difficulty has also been met with in determining exactly how 
much cyanide to use for particular scales and for particular trees, so that the 
scales Shall be killed and the frees uninjured, and this has only been learnt - 
by actual experience. We have, however, overcome this difficulty, and, at the 
end of this article, I have given a long list of the approximate quantities of the 
different materials reauired for different sizes of trees, taking as a basis 1 o7. 
of cyanide of potassium to every 300 cubic fect of space enclosed by the 
tent or sheet. The method of applying the gas is to envelop the tree to be 
treated with a gas-tight covering. These coverings are made of two shapes, 
viz. :—Bell tents and octagonal sheets. The former can be made large enough 
to cover trees up to 10 feet in diameter and 12 feet high, but for trees 
above this size sheets are preferable, as bell tents would be too heavy and 
utiworkable. 
