Aug. 1,1924 
The Greenhouse Leqf-Tyer 
153 
tion of certain other plants owing to 
the danger of bleaching and otherwise 
injuring them.” In a footnote he 
states that Slingerland (13, p. 163-164) 
“ tested this gas against this leaf-tyer, 
and his experiments show that the gas 
does not kill moths, pupae, and grown 
larvae when used at the ordinary 
strength, but only small larvae.” 
Britton (2, p. 370 ) recommends 
fumigation with this gas at the rate of 
0.1 to 0.15 grams of 98 per cent 
gation with dosages ranging from one- 
fourth to one-half ounce sodium cyan¬ 
ide per 1,000 cubic feet of space that 
are ordinarily employed. 
To throw more light on this point the 
experiments recorded in Table IX 
were undertaken with plants harboring 
all stages of the leaf-tyer. 
From the results obtained it is quite 
clear that the moths ultimately suc¬ 
cumb to the above dosage of the gas, 
and may be effectively controlled pro- 
Table IX. —Fumigation with hydrocyanic-acid gas for the control of all stages of 
Phlyctaenia rubigalis a 
Experiment No. 
Date 
Number of 
specimens | 
Observations and results 
I. 
1921 
Apr. 6 
1 
f 36 moths_ 
j 
10 larvae_ 
5 pupae_ 
15 eggs b-! 
Apr. 7,12 moths dead, 24 alive. 
Apr. 8, 21 moths dead, 3 alive. 
Apr. 9, all moths dead. 
No effect, all developed normally. 
No effect, all emerged normally. 
No effect, all hatched normally. 
Control.. 
Apr. 6 
(4 moths._..l 
60 larvae_! 
15 pupae_ 
59 eggs- 1 
Normal, egg depostion continued. 
Normal, developed to pupae. 
Normal, developed to adults. 
Hatched normally. 
II. 
Apr. 25 
15 moths...._ 
Apr. 25, at close of fumigation all moths were lying at 
bottom of cage. 
■ Apr. 26, 9 a. m., 14 moths alive, 1 dead. 
Apr. 26, 3.45 p. m., 5 moths alive, 9 dead. 
Apr. 28, 9 a. m., all dead. 
No effect, all hatched. 
100 eggs- 
Control.. 
Apr. 25 
/144 moths. ..1... 
Normal development. 
Normal hatching. 
\800 eggs- 
a In each of these experiments 1 ounce of sodium cyanide per 1,000 cubic feet of space was used with an 
exposure to the gas lasting 1 hour, and at temperatures of 73° F. and 76°, respectively. 
6 These eggs were deposited by the moths just prior to fumigation. 
potassium cyanide for each cubic foot 
of space (or 3.5 ounces per 1,000 cubic 
feet). Expressing this dosage in terms 
of sodium cyanide (which is now 
generally used for fumigation pur¬ 
poses), it would be equivalent to 2.64 
ounces of sodium cyanide, an amount 
greatly in excess of dosages which can 
be safely employed for general green¬ 
house fumigation. 
Moreover, results of recent experi¬ 
ments indicate that the egg, larval, and 
pupal stages are not affected by fundi¬ 
vided the plants concerned can tolerate 
it. Furthermore, no egg deposition 
took place from the time of exposure to 
the gas until the death of the moths. 
The larvae and pupae developed nor¬ 
mally and were not affected by this 
treatment. Moreover, pupae placed in 
a cyanide bottle from one-half hour to 
24 hours emerged later as normal moths. 
All controls developed normally. 
Incidentally, fumigation with to¬ 
bacco has proved ineffective against 
any and all stages of the insect. 
