220 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 17 
ounce, without severe injury unless the plants are protected from sun¬ 
light for a period greater than 48 hours after treatment. 
Incidentally it might be well to mention the fact that during the 
above tests the 1 and 2 ounce dosages per 1,000 cubic feet were repeated 
in order to verify the results of the previous season on the effectiveness of 
these dosages against the eggs of Pseudaonidia duplex at temperatures 
ranging from 46° F., and higher. Since crawlers hatched at the 1 
ounce strength it indicated that it is not effective during low tempera¬ 
tures. 
Miscellaneous Results with Hydrocyanic-Acid Gas 
Additional data has been accumula ed at intermittent periods during 
the year on the efficiency of this gas, some of the outstanding results of 
which are as follows: The 2ounce rate killed 100 per cent of the soft 
brown scale, Coccus hesperidum (L), and the chaff scale, Parlatoria 
pergandii Comst., but was only partially effective in controlling larvae of 
the azalea leaf roller or miner, Gracilaria azaleella, and the azalea bark 
scale Eriococcus azaleae Comst. Results of plant tolerance experiments 
indicated that poinsettias when the bracts had developed their intensity 
of red color can stand as high as ounces, and that azaleas may be 
fumigated as high as the 5 ounce per 1,000 cubic feet rate although it 
caused tip burning of one variety. 
Calcium Cyanide as a Greenhouse Fumigant 
During the past summer samples of calcium cyanide in granular and 
dust form were received from Dr. Wm. Moore and experiments were 
undertaken to determine their value as greenhouse fumigants. Pre¬ 
liminary experiments in a 200 cubic foot box with the dust were made 
and more recently similar tests were conducted under actual greenhouse 
conditions. In the box tests the calcium cyanide dust was spread over 
damp newspapers in amounts equivalent to from one-half to one ounce of 
sodium cyanide per 1,000 cubic feet and the plants were exposed for one 
hour to the gas evolved. Two species of aphids were used viz: Macro- 
siphoniella sanborni on chrysanthemums in experiments 1 to 9, and 
Illinoia pelargonii on geraniums in experiment 10. Vinca, Jerusalem 
cherry, Martha Washington geranium, begonia, and Kentia palms were 
also included and escaped injury. The ounce rate caused slight tip 
burning on Lantana and snapdragon, and the 1 ounce rate on chrysan¬ 
themums. These results are shown in Table II. 
