19, 2 
Lee: Citrus-canker Control 
135 
cent formalin solution to avoid infection, but the recommen- 
dation apparently was not based upon experimental evidence. 
Spraying experiments upon Washington navels in Japan have 
been reported by several Japanese investigators and were 
apparently successful to some degree as practiced by the inves- 
tigators. Growers of Washington navels in Japan at present, 
however, have given up such spraying as unsuccessful in a 
number of cases. A more detailed review of the Japanese liter- 
ature will be presented in a later publication. 
THE CONTROL EXPERIMENTS OF THE PRESENT INVESTIGATIONS 
DESCRIPTION OF METHODS 
Lime sulphur solution, Bordeaux 4-4-50 mixture, and Bur- 
gundy 3-3§-50 mixture 3 are so commonly used that no discus- 
sion as to the methods of preparation is necessary. During 
the spraying experiments it seemed desirable to attempt to 
render the copper more readily available for action against the 
canker organism, following the theory 4 of Bedford and Pick- 
ering; (l, 2) in the case of Bordeaux mixture the excess of lime 
was, therefore, reduced to just the amount sufficient entirely 
to precipitate all of the copper. This was called neutral 
Bordeaux mixture. A similar neutral Burgundy mixture was 
employed in which the sodium carbonate added was just 
sufficient to precipitate the copper with no excess remaining. 
Ammoniacal copper carbonate solution, when used, was made 
up to contain: Copper carbonate, 5 ounces; concentrated am- 
monium hydroxide, 3 pints; and water, 50 gallons. The 
methods of preparation are, of course, well known. Formalin 
as a preventive was used as a simple solution, easy to pre- 
pare; neutral lead arsenate is also so commonly used as to need 
no discussion. 
Two different oil-emulsion preparations were used in check- 
ing scale-insect increases following the fungicide applications. 
An oil emulsion described by Yothers(22) was commonly used. 
This consisted of soft soap, 4 pounds; paraffin oil (25° Baume), 
1 gallon; and water, 1 gallon. The preparation was made up 
in the ratio of 1 gallon of the mixture to 50 gallons of water. 
Another oil emulsion consisted of a mixture of a cresylic soap 
liquor with kerosene or distillate. This emulsion was prepared 
8 The spraying experiments reported here were begun and carried to a 
conclusion before the work upon the phenol coefficients of fungicides (ID 
with the canker organism had been completed. 
4 These references have not been available in Manila but are quoted from 
their reviews. 
