Vol. L1X. No. 2610. 
NEW YOKE, FEBRUARY 3, 1900. 
$1 PER YEAR. 
THE USE OF HYDROCYANIC ACID GAS. 
FOR KILLING INSECT PESTS AND VERMIN. 
Us Usa Outdoors and in Buildings. 
Part III. 
IN GREENHOUSES.—As previously indicated, this 
gas was first used for outdoor fumigating, and later 
for greenhouse work, then extensively in the nursery. 
The greenhouse problem in reference to insects, has 
been one of considerable importance, and early in 
1895, Professor Albert F. Woods and Mr. P. H. Dor- 
sett, of the Division of Vegetable Pathology, United 
States Department of Agriculture, began a series of 
experiments under glass with this gas. They found 
that plants were less injured by a short exposure to a 
relatively large amount of gas, than they were by a 
long exposure of a relatively small amount. It was 
also shown that the stronger dose a short time was 
most destructive to the insects affecting the plants. 
In these experiments they showed that different species 
and varieties of plants varied remarkably in their 
power to withstand the gas, depending upon the open 
or closed condition of the breathing pores of the leaf, 
the cell contents, and temperature of the inclosure. 
The plants fumigated were ferns, Coleus, double Eng¬ 
lish violets, single violets, roses, carnations, grapes, 
tomatoes and cucumbers. The amount of cyanide 
used per cubic foot of space inclosed varied from 
0.075 gramme to .15 gramme. For instance, ferns, 
infested with a scale insect, similar to the Scurfy scale 
on apple, were fumigated at night with 0.075 gramme 
98 per cent cyanide for 20 minutes without injuring 
the most delicate fronds, at the same time destroy¬ 
ing all the insects. In case of Coleus, infested with 
Mealy bug, in a very large house (15,587 cubic feet), 
one-tenth (.10) gramme cyanide was used. In case 
of the double English violets, infested with plant 
lice, slugs, millipedes, leaf-eating larvae, 
cutworms, Red spider, etc., fifteen hun¬ 
dredths (.15) gramme was used, and ex¬ 
posed 20 minutes. All the insects were 
destroyed, excepting a few Red spiders, 
and even these were kept down by fre¬ 
quent fumigation. 
FOLIAGE EFFECTS.—The foliage of 
single violets, like California, Princess 
of Wales, and the like, is sometimes 
slightly injured, with the stronger dose 
(.15); a weaker amount, one-tenth (.1) 
gramme should be used for these single 
varieties. Roses, especially the younger 
growths, are very sensitive, and slight 
injury has been noticed even where the 
smallest dose (0.075 gramme) was used. 
Carnations will stand one-tenth (.1) 
gramme for 15 minutes; but more care¬ 
ful experiments are needed before the 
gas is generally recommended for either 
carnations or Chrysanthemums. Grapes, 
under glass, in New Zealand, have been 
fumigated at the rate of nine-hundredths 
(.9) gramme over night, infested with 
Mealy bugs, with good results. It has 
also been used successfully by Dr. Jabez Fisher on 
tomatoes infested with the White fly (Aleyrodes sp.). 
He used one ounce cyanide (28.35 grammes) for 1,000 
cubic feet, and left the plants exposed over night with¬ 
out injury. Last Fall one of our greenhouses here, 
in which cucumbers were growing, became badly in¬ 
fested with the Cucumber or Melon louse, (Aphis 
gossypii). We filled the house with gas at sundown, 
using fifteen-hundredths (.15) gramme of cyanide per 
cubic foot, and left it until morning. The lice were 
destroyed, and no perceptible injury was done to the 
plants. Indian corn, from 10 to 12 inches high in pots 
standing in one end of the house for experimental 
purposes, was destroyed. 
QUANTITY FOR GREENHOUSE USE.—In all 
greenhouse work, the cubic contents of the house must 
be determined accurately and multiplied by the frac¬ 
tion of a gramme per cubic foot to be used. For ex¬ 
ample, one of Woods’s and Dorsett’s houses contained 
4,646 cubic feet. To fumigate it, using fifteen-hun¬ 
dredths (.15) gramme per cubic foot, we multiply 
4,646 by .15, which equals 696.9 grammes, which, re¬ 
duced to ounces (28.35 grammes=one ounce) by di¬ 
viding by 28.35 equals 24.58 ounces avoirdupois, or 
'FUMIGATING BOX SHOWING COLEUS CUTTINGS. Fro. 21. 
practically 24*4 ounces of cyanide. The acid is now 
easily estimated, using one-half more acid (liquid 
measure) than cyanide, thus: 24 x 12 = 36 ounces acid; 
and a half more water than acid, thus: 36 x 18 = 54 
ounces water. A house, therefore containing 4,646 
cubic feet, for .15 gramme per cubic foot, needs 24% 
ounces (weight) cyanide, 36 ounces (liquid measure) 
sulphuric acid, and 54 ounces water. The chemicals 
are prepared in exactly the same manner as described 
for nursery fumigation in the first article; except, 
that the cyanide is suspended over the vessels contain¬ 
ing the acid and water in a paper bag by means of a 
string arranged for that purpose, and leading to the 
door, as shown in Fig. 22. When all is in readiness, 
at night, the bag of cyanide is gradually lowered in 
the vessels, the doors closed and left the desired 
length of time. Remember all the cautions cited in 
the first article. 
TO FUMIGATE CUTTINGS, such as Coleus, etc., 
construct a good tight box, the size depending upon 
the number of plants used. A box containing from 25 
to 50 cubic feet of air space is a convenient one, and 
can be used for fumigating individual plants in pots 
when necessary. My attention was recently called to 
a lemon tree about three feet high, in a conservatory 
where it was not desirable to remove it. I suggested 
that a box be prepared to cover it, and I would esti¬ 
mate and furnish the chemicals necessary for fumi¬ 
gation. The tree was fumigated at night for half an 
hour with .16 gramme cyanide per cubic foot, and the 
scales were destroyed “as if by magic.” 
THE BOX USED by Woods and Dorsett is shown 
in Fig. 21. It had a tight-fitting lid, and a small door 
at bottom for admitting the chemicals. It was so 
constructed that several trays, covered with wire, con¬ 
taining cuttings, could be fumigated at one time. As 
a rule, it is desirable to keep the plants, especially 
cuttings, 10 to 12 Inches above the vessel containing 
the chemicals. There is much to be learned about 
the physiological effect of this gas upon many plants 
yet, and we would like to hear from anyone who has 
had any experience along this line, when the exact 
amount of chemicals and cubic space are known. In 
our next and concluding paper of this series we will 
consider the use of this gas in various inclosures for 
the destruction of Insects and vermin. 
Maryland Exp. Station. [prof.] w. g. Johnson. 
R. N.-Y.—There was a lively debate at the meeting 
of the Western New York Horticultural Society over 
the best methods of fighting the San Jos6 scale. The 
R. N.-Y. last week took a vote of many influential 
members of the Society, and found that a large ma¬ 
jority favored a law compelling the fumigation of 
nursery stock. Some nurserymen and others opposed 
this stoutly, the chief argument being that they did 
not consider such fumigation necessary. The follow¬ 
ing resolution was finally passed: 
Resolved, That the 500 members of the Western New 
York Society now assembled, would unite In urging the 
Legislature now in session to enact such laws as shall 
compel inspection and treatment or destruction of all in¬ 
fected trees and to compel the fumigation of all nursery 
stock raised or brought into the State or offered for sale. 
Our judgment is that five years hence 
the Society will realize that it made a 
mistake in not strongly demanding a 
law like that now in force in Maryland, 
which makes fumigation compulsory. 
One influential member of the Society, 
who wrote before the meeting that he 
did not consider the matter serious 
enough to warrant any strict laws, now 
says that he must change his views. He 
now writes: 
Since attending the Horticultural Society 
meeting at Rochester, and talking more 
fully with others, I think it is becoming 
much more serious than I had previously 
judged, and I am inclined to think that it 
would be well to provide that all nursery 
stock subject to it should have treatment 
before sending out, that will destroy any 
possible San Jos6 scale. I also think that 
provision should be made to eradicate it 
from orchards and other fruit plantations 
where it exists. 
We feel sure that there are many like 
this man, who, when they realize the 
gravity of the situation, will be fully in 
favor of restrictive measures. It is a 
mistake to attempt to scare the people, 
for that will do more narm than good, 
but the sensible thing to do is to realize the situation 
now, and face it like grown-up men. The nurserymen 
in Maryland all say that the law compelling fumiga¬ 
tion has been helpful to them. This is just what we 
should expect, for a certificate of inspection is by all 
odds the best present guarantee of clean stock. At 
present nurserymen give a certificate of inspection— 
a printed circular, stating that the State entomologist 
has examined some trees in the nursery. To show 
how little this amounts to, it was stated at Rochester 
that stock had been received which was alive with 
the scale, although in a package bearing the inspec¬ 
tion certificate. We feel sure that well-informed grow¬ 
ers will soon settle the matter by refusing to buy 
Stock that has not been fumigated. 
