THE GARDENING WORLD 
337 
April 23, 1904. 
[Some prizes were offered by Mr. John Crook, Forde Abbey, 
Chard, for an essay on the Potato', by students attending an 
evening continuation class: at Winsham, Chard. First prize 
was awarded to Edwin Forsey. The competition was limited 
to those from fourteen to sixteen years of age.—E d.] 
Cyaniding on an Established Basis. 
Considering the great value attached to the use of “ cyanide ” 
or hydrocyanic acid gas in the United States for the destruction 
of insect pests on fruit trees in the open air, it seems scarcely 
conceivable that the practice should have remained for so long- 
more or less a mystery rather than, a true Mend to the growers 
of this country. Vague recommendations have been set forth 
from time to time as to' the strength and materials to be used. 
But. in many cases the results which followed were as de¬ 
structive to plant life as toi the insects themselves, wliile in 
other cases both escaped uninjured. This clearly demonstrated 
the want of true knowledge regarding the properties and uses 
of hydrocyanic acid gas as a fumigant in this country. The 
conditions prevailing here are totally different toi those abroad, 
and it was recognised that to be successful it must be adapted 
to meet our requirements. 
With a view to arriving at these requirements and placing 
the operation of “ cyaniding ” from an experimental to an 
established basis, a series of tests were carried out at the 
Gardens of the Royal Botanic Society. One large range 150 ft. 
long, 20 ft. wide, and 13 ft. high was successfully done:, and 
followed by a smaller one. In these ranges plants infested 
with mealy bug, thrip®, red spider, scale, greenfly, etc., were 
collected, and in the short space of two hours from start to 
finish all the above pests were completely destroyed without 
injury to plant life. 
The preparations consisted of arranging all ventilators 
doors, etc., to. open from the outside, and safely fastening the 
same to prevent any person entering during the operation. 
The amount of cubic air space having been previously cal¬ 
culated and 1,000 ft. adopted as a unit, the proper proportions 
of cyanide and sulphuric acid required were to hand ready for 
use. Shallow earthenware pans were: adopted as generators, 
and into these the required volume of water and sulphuric 
acid were placed respectively. Boards about. 11 in. wide and 
5 ft. long were hung over each generator for the purpose of 
evenly distributing the gas, and are worked by attached cords 
from exterior of house during generation. The cyanide is 
then arranged in a shallow tin, with a special tipping arrange¬ 
ment attached to the air fan. After carefully placing the. 
cyanide tins in proper position, beginning at farthest end of 
house and finishing near door, the operator leaves the structure 
and makes the door fast. 
Til© fans are then started, the cyanide tipped and gas rapidly 
generated. The air fan should be worked for a period not 
exceeding ten minutes, and fivei is ofttimes sufficient. The time 
of commencing to generate gas is noted and the period of 
exposure commences. This varies according to the tempera- 
ture, atmospheric moisture, nature and condition of plant and 
pests to be destroyed. 
At the expiration of this period the ventilators and doors 
may be opened and fully cleared from gas before any person 
is allowed to enter. No person must either remain in the 
building after mixing the cyanide and acid, or enter until 
quite clear. Materials of standard quality should be used, and 
the English method of using “sodium cyanide” in place of 
potassium cyanide should be adopted. Better results are 
obtained by doing this, and the cyanide is of an even quality 
and a more concentrated form. This is known as the: “ Straw- 
son sodium cyanide process,” invented by Mr. G. F. Strawson, 
who., in conjunction with Mr. W. F. Emptage and myself, 
carried out and recorded the experiments. Other tests carried 
out in Messrs. Ladds’ Nurseries at Swanley, in Scotland, and 
c sew here on the above l ines thoroughly endorse our opinion 
as to the value of “ cyaniding ” when carefully carried out. 
The following “ proportions and uses ” have been drawn up 
by Mr. AV. F. Emptage, and endorsed by myself : — 
Proportions and Uses for 1,000 ft. unit. 
(1) . Tor nurserymen in clearing dormant stock of outdoor 
shrubs and trees of scale, American blight, etc.,, the plants 
should be stood thickly together in a glasshouse or in a 
cyaniding shed, which should become part of thei outfit of every 
nursery place; 2^ oz. of the sodium cyanide, 130 per cent, 
strength, 5 fluid oz. sulphuric acid specific gravity 1.8, 15 fluid 
oz. water, will be ample: for the purpose; 50 to 60 minutes may 
be given as the period of exposure. Tire trees will be best dry 
and the temperature of the shed at about 50 deg. 
Nurserymen buying in stock from fresh places, where scale, 
etc., are found on them or are to be feared, should always 
subject the: plants, etc., to this process 1 . The formulae given 
will also be found useful for all kinds of forest trees when 
dormant. 
(2) . For the destruction of all scale insects 1 , mealy bug, 
thrip'S, etc., on A ines when the fruit is cut, and on Peaches and 
Nectarines when the fruit is cleared, and on. Orange trees, 
Camellias, Gardenias, Steplianotis, Passifloras, Dipladenia®, 
Palms, Plumbago', Euphorbias, Orchids:, Fuchsias, Azaleas, 
greenhouse Rhododendrons, Rose®, hard-leaved Ferns, Ficus 
and many other subjects, when not actually making a new 
growth. 
Orchids may be cyanided safely when the roots are not 
making new growth on the outside of the baskets or in the air. 
No grower or nurseryman need be troubled with mealy bug 
again. For these plants:, in a temperature of 50 to- 55 deg., 
2 oz. sodium cyanide:, 4 fluid oz. of sulphuric acid, and 12 fluid 
oz. of water, exposure 40 minutes, will be perfectly safe quanti¬ 
ties to' use. The foliage should be diy, but this is not impera¬ 
tive in the case of dormant plants. 
For Vineries in Winter. —At or about pruning time, when 
the Arinas are quite dormant, for the destruction of Vine scale, 
mealy bug, red spider, etc., two: cyanidings should be given at 
intervals of 24 horn’s of 24 oz. sodium cyanide, 5 fluid oz. sul¬ 
phuric acid, 15 oz. water, exposure 50 minutes, temperature 
of house 50 to 55 deg. 
Fly and other Insects among G owing Plants. —For all 
plants such as Pelargoniums, when not in flower, Azaleas and 
general greenhouse stuff, 14 oz. sodium cyanide, 34 fluid oz. 
sulphuric acid, 104 fluid oz. water may be used with perfect 
safety, providing tire plants are dry and the temperature of the 
house not above 55 deg.; exposure 40 minutes. 
For Fly, Thripq etc., on more delicate subjects.-—14 oz. 
sodium cyanide, 3 fluid oz. sulphuric acid, 9 oz. water, ex¬ 
posure 40 minutes. The plants should be quite dry and the 
temperature be lowered to 55 deg. if possible. Where this is 
not possible- 1 oz. of sodium cyanide will probably be sufficient, 
2 fluid oz. sulphuric acid, 6 o-z. water, repeating the operation 
if needed. 
Tomato Fly (Aleyrodes).- This is a- pest that, only those who 
have large Tomato houses infected can fully comprehend. 
There need be no further trouble in this respect, as- the 14 oz. 
formulae.(No-. 2) will bring everyone down to- death. Repeated 
every two days until all eggs are hatched, there will be a 
thorough clearance made. 
There is no other method of insect destruction, especially for 
Amines, etc., that is so cheap and efficient as the sodium cyanide 
process. 
AVe- shall be pleased to- give advice: on the use of the gas to 
all who need it. Elderbert F. Hawes. 
Royal Botanic Gardens, Regent’s Park, N.AV. 
High Price for Potatos.- —Table Potatos axe being retailed 
in AVigtown and locality at the high rate of 10s. per stone, and, 
in respect of this quotation, merchants maintain that they can¬ 
not be bought wholesale under £5 per ton. When Potatos are 
abnormally high in price more bread is used, and the demand for 
Potatos is hence restricted 
