June, '24] 
LEACH, FLEMING AND JOHNSON: INSECTICIDES 
363 
water and the degree of agitation while preparing the solution. In view 
of this incompatability the writers carried on an extensive study of the 
emulsification of carbon bisulphide in order that the dosage might be 
controlled. The work involved the testing of the hydrophile colloids as 
emulsifying agents. It was found, in common with other investigators 
on this subject, that soap was by far the best emulsifying agent—es¬ 
pecially the rosin-fishoil soaps. In the absence of standard brand soaps a 
stable emulsion can be made by the use of sodium or potassium oleate, 
or some other higher fatty acid. 
With carbon bisulphide, emulsified by these methods and capable of 
being measured accurately and dispersed in water, the compound was 
tested upon various types of plants which were quarantined or in danger 
of being quarantined. The work, in addition to the study of the factors 
influencing the larval kill in the soil, included the experimental treat¬ 
ment of French hydrangeas, Japanese azaleas, rhododendrons, blue 
berries, ferns and other plants. It was found that plants in general 
would withstand a dose of the emulsified compound greater than that re¬ 
quired to control the insects present. In the case of French hydrangeas 
a concentration of 0.5, 0.625 cc. of emulsified carbon bisulphide per liter 
of water controlled the insect in the soil when a volume of solution equal 
to one-half the volume of the treated soil was applied. The plants were 
growing in a sandy soil low in organic content and were treated by 
placing galvanized iron collars in the soil, applying the required amount of 
solution and allowing it to drain into the soil. At the end of 48 hours, the 
plants were dug, potted in wooden tubs and placed in the greenhouse. 
The tops of the plants remained normal while the feeding rootlets were 
sheared off by the action of the chemical. Within two weeks the plants 
had replaced these feeding rootlets and resumed a normal growth. 
In other words the plants experienced a temporary check in growth due 
to the action of the compound on the roots but rapidly recovered and re¬ 
sumed growth with a varying degree of stimulation. 
In the case of Japanese azalea, rhododendron, blue berry, fern and 
other ericaceous plants which prefer an acid soil containing an abundance 
of peat, it was found that the amount of emulsified carbon bisulphide 
necessary to secure complete insect mortality depended upon the amount 
of organic matter present and that in every case the plant had greater 
resistance than the insect. Employing this method the writers have to 
date successfully treated 1,500 cibotium and aspidium ferns belonging to 
one of the local nurseries and valued at $10,000. Experimental data is 
now at hand to insure the successful treatment of azaleas, rhododendrons, 
