442 
THE DICTIONARY OF GARDENING, 
Insecticides—continued. 
too, the time at which Insecticides may be most effec- 
tively used will vary with the species. Take the Scales. 
To spray on an Insecticide when the Scale-like coverings 
of certain species have been formed, avails but little: the 
time is when the newly-hatched larve are on the wander. 
Timely application of Insecticides is very important, 
and this is especially the case with crops which are 
destined for market or the table, when appearance is 
everything. Insects on outdoor crops are, as a rule, 
more difficult to control than those on indoor ones. A very 
important point in connection with any Insecticide is to be 
certain as to its effect upon any plant before applying it 
wholesale. An indiscriminate application upon a tree or 
plant may lead to disaster. 
For poisoning the food-plants of chewing insects like 
the lary of Moths, Butterflies, and Sawflies, the grubs 
of Beetles which feed exposed, as well as the Beetles 
themselves that lay the green parts of plants under 
contribution, Paris Green (despite the prejudice against 
its use), in the proportion of loz. to 20 gallons of water, 
is the best Insecticide. Many growers also add loz. of 
lime, as this minimises the chances of the foliage being 
injured. The mixture should be kept stirred, or the 
Paris Green will settle, and it shonld be distributed 
in a nice fine spray. With frnit trees on no account 
should the preparation be employed when they are in 
blossom. So far as the fruit itself is concerned there is 
not the slightest danger to the consumer if the arsenite 
is used in the proportion stated. Manufacturing agri- 
cultural chemists, like Mackey and Mackey, of Bermondsey, 
keep Paris Green Paste ready for making the Insecticide ; 
and this is preferable to having to mix the powder one’s 
self, an operation fraught with not a little risk. London 
Purple is another powerful arsenical poison, and needs to 
be just as carefully handled. 
Hellebore (in powder) dusted or blown on to the trees 
in the early morning is also a capital Insecticide, 
especially in the case of the Sawfly and Caterpillar 
grabs on Gooseberries. Although a strong poison, Helle- 
bore is soon rendered harmless by contact with the out- 
side air, and must therefore be renewed. 
For sucking animals, one of the best all-round 
preparations is Kerosene (paraffin) Emulsion. If properly 
made the kerosene does not separate and cause injury 
to the plants. It may be procured in this country in a 
concentrated form, and all that the user has to do is 
to dilute it to the proper proportions, which wil! vary 
somewhat with the kind of tree under treatment and 
the age of the leaves. The ingredients are hard or soft 
soap, kerosene, and rain water. Their proper amalgama- 
tion requires some skill. 
weaker the solution. The exact proportion may be deter- 
mined by the gardener himself. These emulsions are best 
bought from firms with the machinery for making them. 
A very good home-made preparation for similar insects 
consists of 1 wineglassful of ordinary petroleum and 3 
gallons of hot water. The difficulty about this solution is 
that the petroleum does not readily amalgamate, and 
constant stirring is necessary. It is a very good plan to 
put sufficient soff soap in the water to discolour it, as 
this has been fonnd preferable to plain water. 
Soft soap alone is a capital Insecticide for Scale. 20z. to 
a gallon of hot water may be safely employed upon hard- 
wooded greenhonse subjects, but upon softer things the soap 
may be reduced one-half. For rubbing into the bark of 
trees it may be used at from three to four times the 
strength of that first named. 
Water applied at a temperature of 140deg. is a most 
useful Insecticide, especially for Scale. It has the merit, 
too, of being harmless to the plants under treatment— 
neither leaves, flowers, nor fruits being affected. Aphides 
readily succumb to it, as do Thrips. In the case of 
Cactuses suffering from insect pests—Mealy Bug, &c.— 
the hot-water treatment may be very successfully 
employed, first turning the plants on their sides. The 
great difficulty is in keeping the water sufficiently hot: it 
quickly cools on delivery. 
Hard-bodied insects, like many of the Beetles, are 
difficult to cope with where they do not actually feed 
upon the green portions of the trees or plants, their 
horny wing-cases protecting them against the Insecticides 
which kill by contact and that may be safely employed. 
Many of the most troublesome Weeryils, all of which are 
The younger the foliage the - 
Insecticides—continued. 
night feeders, are best shaken on to a board thickl 
smeared with tar and afterwards collected and destroyed. 
Earwigs, Cockroaches, Ants, Wasps, and Wood-lice 
are best dealt with by traps or poisoned food. Red 
Spider (including the Bryobias) shonld be killed by 
contact when on outdoor trees ; while indoors they should 
be treated to one of the vaporising Insecticides, except in 
the case of certain Grapes. 
Fumigation by means of hydrocyanic acid gas is likely in 
the future to prove of immense benefit against many pests, 
as in the case of Currant-Bud Mite (which ais and 
some of the worst kinds of Scale. For years the former has 
baffled all the efforts of gardeners and economic entomolo- 
gists to stay its ravages. From some extensive experiments, 
however, made by Mr. H. H. Cousins, M.A., Mr. A. V. 
Theobald, M.A., and others at the Wye Agricultural 
College, there is no doubt that the formidable foe may be 
ousted by the powerful Insecticide named, and a fall report 
of the experiments appeared in the ‘‘Gardeners’ Chronicle.” 
Nearly twenty years ago this Insecticide was used in 
California for the destruction of Scale in the Orange 
groves, and proved of immense benefit. Great care 
has, however, to be taken that the fumes are not inhaled. 
So far as the Currant-Bnd Mite is concerned, the best 
time for fumigation appears to be December and January. 
The cost is infinitesimal. In California tents are used 
for surrounding the infested trees; while in the experi- 
ments conducted at Wye a modification of this plan by 
the use of a waterproof cloth seems to have been 
employed. loz. of cyanide to 150 cubie feet Mr. Cousins 
and his colleagues found effectnal. 
The following is the formnla for making the hydro- 
eyanie gas: Cyanide of potassium, loz.; sulphuric acid, 
20z.; water, 30z. The water is placed in a glazed earthen- 
ware vessel (an old jam-pot, for instance), and then the 
acid is put in; the waterproof tent or material is then 
placed, round the bushes or trees to be freed, and the 
cyanide added. There is no necessity to go to great 
expense with the ‘‘tent.” Mr. D. W. Coqnillet, who was 
the first to discover the merits of hydrocyanie gas as an 
Insecticide, simply employed common bed-ticking treated 
with linseed oil. The covering is left round the tree for 
half to three-quarters of an hour. 
Hydrocyanic gas has also been successfully employed 
as a greenhouse Insecticide in New South Wales, and it 
was found that not only did it destroy Thrips and Red 
Spider, but Scales, Ants, and Beetles. Still greater care 
would have to be exercised in a greenhonse, and the 
cyanide would haye to be first suspended and controlled 
by a string from the outside, so that it could be dropped 
at the right moment. Several conditions are necessary, 
according to Mr. Hugh Dixson, who contributed a most 
practical article upon the subject to the ‘‘ Gardeners’ 
Chronicle.” These are that the foliage of the plants be 
dry, that the wind is blowing away from any private 
residence, and that no persons are near the house at the 
time it is being treated, especially upon the lee side; 
and finally, that all vessels that the cyanide has touched 
be carefully washed and the water thrown down the sewer. 
Mr. Dixson says that 1 grain of cyanide for every cubic foot 
of the house, and an eqnal quantity of sulphuric acid 
diluted with an equal quantity of water, are the proper 
proportions. 
Carbon bisulphide is employed for root-feeding insects 
like Schizoneura lanigera, found upon the roots, as well 
as the trunks and branches, of Apples, &c.; the Grape 
Phylloxera (which see); and the Cabbage Gall Weevil. 
Doubtless its sphere of usefulness may be considerably 
extended. 
Borax is frequently used with success in plant-honses 
where Cockroaches abound, but rather as an expellent 
than as an Insecticide. In California, Resin Washes are 
much used for Scale, and they prove very effective ; but 
in England and in other countries such washes are not 
called for. Resin Washes usually consist of resin, caustic 
soda, tallow or oil, and water; and less often paraffin. 
Of the more recent commercial preparations for use in 
glasshonses, those known as yaporising Insecticides, like 
Nicoticide, XL All, and the like, are of great value if 
used with caution, and to a very great extent they have 
simplified the work in connection with the pests of stoves, 
greenhouses, conservatories, and fruit-honses. They are 
mostly tobacco preparations. 
