46 BULLETIN 885, U. S. DEPARTMENT OE AGRICULTURE. 
Preliminary spray work, however, has been done during the rainy 
season with 5 and 10 per cent kerosene emulsion, fish-oil soap at the 
rate of 1 pound to 2 and 4 gallons of water, and nicotine oleate at 
the rate of 1 part of nicotine to 500 parts of water. 
The kerosene emulsion stock solution was prepared according to 
the following formula: Kerosene, 1 gallon, laundry soap, 10 ounces, 
and water, 1 gallon. When agitated in an ice-cream freezer or similar 
device this formula makes an excellent emulsion and has the advan- 
tage that it can be readily diluted to any percentage without the use 
of complicated mathematical formulas. Thus to obtain a 5 per 
cent solution it is diluted with 18 parts of water since it already con- 
tains 1 part of the 19 necessary to make a total of 20. 
Both the 5 and 10 per cent emulsions were effective controls though 
the 10 per cent emulsions caused some burning and were therefore dis- 
continued. The 5 per cent emulsions proved very effective, and trees 
were completely freed from A. woglumi by one or two sprays. If two 
sprays were used they were given at intervals of one week. 
The preliminary tests of fish-oil soap sprays were a decided surprise 
in that two sprays either at the rate of 1 pound to 2 gallons or to 4 
gallons of water at intervals of one week completely freed trees not 
only of A. woglumi, but also of such scale insects as Pseudaonidia 
(Selenaspidus) articulatus Morg., ChrysompJialus aonidum Linn., and 
Pseudococcus sp. without causing injury. 
The nicotine oleate was prepared according to the formula given 
by Moore (20). In the case of this spray it was necessary to apply 
it three times at intervals of a week before the trees were freed from 
all stages of the black fly. 
Since all this work was done in the rainy season the efficacy of a 
spray was determined in two ways, (1) by counts made on large 
numbers of individuals in various stages of development and determin- 
ing the numbers that were dead and alive, and (2) by the numbers 
of individuals that would " slough" or wash off during the heavy rains. 
It was found that when a spray was really effective practically all 
the dead black flies as well as the scale insects would be washed off 
during the heavy tropical rains, whereas on check trees or on those 
where the spray was a failure this did not take place. 
The formulas recommended by W. W. Yothers for the control 
of the citrus white fly (Dialeurodes citri Ashmead) have not yet been 
tried owing to absence of suitable cheap oils of the type he recom- 
mends. However, in view of the success that has so far been 
obtained with both the kerosene emulsions and fish-oil soap sprays, 
the sprays recommended by Mr. Yothers should prove even more 
effective due to the fact that their "high boiling point and great vis- 
cosity make them operative over a longer period of time after appli- 
cation, and, too, they are only slowly affected by average temperature 
and showers." 
