June, ’24] 
WEIGEL AND BROADBENT: OIL EMULSION 
389 
placed at our disposal to conduct these investigations. In addition to 
Kentia palms this house also contained such ornamental plants as 
Phoenix rupicola, Aspidistra lurida, Ficus elastica, Laurus nohilis , 
Aucuba Japonica, and Citrus sp., all of which were infested. 
For the purpose of determining the possibility of increased control and 
the probable limits of plant tolerance, several plants were sprayed with a 
more concentrated emulsion. A single treatment with either a 1:32 or a 
1:25 “boiled” emulsion killed 100% of the scale insects, but unfortunately 
it also impaired the ornamental value of the foliage by leaving it greasy, 
and, in the case of palms, causing the fronds to turn yellow. 
To verify previous work with the 1:50 “boiled” emulsion, a mis¬ 
cellaneous group of plants growing in the palm house under normal green¬ 
house conditions was sprayed once, on June 14, using a 24-gallon Deming 
Sprayer equipped with a disk nozzle. From the results of experiments 12 
to 15 inclusive, it is quite evident that very satisfactory control can be 
obtained from one application of this insecticide. In view of the fact that 
no injury had developed on these plants within seven weeks after treat¬ 
ment, the remainder of the plants was then sprayed twice in succession, 
viz, August 3 and 29 with a 1:50 boiled emulsion. 
Final observations on the effects of two applications of the “boiled” 
emulsion are given in the table under experiments 16 to 19. In this 
connection it should be noted that scales found alive had apparently es¬ 
caped contact with the insecticide even after two treatments. For ex¬ 
ample, most of the living scales listed in experiment 17 occurred in a 
group within a folded section of Aspidistra leaf. Also in experiment 18 
live scales were found only on the smooth upper surface of a citrus leaf to 
which the emulsion had apparently failed to adhere. The plants have 
shown no evidence of injury from these treatments. 
Assuming that two or three treatments at close intervals would insure 
complete control, it is doubtful whether the difference in effectiveness 
would be sufficient to justify the additional expense of application and 
the greater risk of injury. The results of these investigations demon¬ 
strate that spraying once with a 1:50 “boiled” lubricating-oil emulsion, 
provided it is thoroughly done, will give a very satisfactory control of the 
Florida red scale, Chrysomphalus aonidum Linn, without injury to hardy 
ornamental greenhouse plants. 
