20, 2 Lee and Shino: Citrus-canker Control Experiments 133 
foliage infections were to be observed; no infections were observed on the 
fruits. Three trees of the formalin plat showed a considerable amount of 
new foliage infections but no fruit infections. 
A careful examination was made for indications of an outbreak of ruby 
scale but no signs were visible at this time. If the scale insects remain 
as they are, without perceptible increase, the insecticide application planned 
for the latter part of July will be omitted. 
Leaf samples were brought back to Nagasaki and tested for the amounts 
of copper remaining on the foliage. The test used was the method de- 
scribed by Winston and Fulton:(7) dissolving the copper compounds on 
the leaves in a dilute nitric acid solution, testing this wash solution with 
potassium ferrocyanide, and comparing the resulting color formed with the 
coloration formed in solution having a known copper content. The results 
were as follows: 
Bordeaux 4~-4—50 applied June 24; tested July 2, 50 m. g. Cu per 100 
grs. of leaves. ; 
Bordeaux neutral applied June 24; tested July 2, 40 m. g. Cu per 100 
grs. of leaves. 
Burgundy 3—3-50 applied June 25; tested July 2, 40 m. g. Cu per 100 
grs. of leaves. 
These results should be compared with tests made June 17 on the ad- 
herence of copper sprays, as follows: 
Bordeaux 44-50 applied June 5; tested June 17, 45 m. g. Cu per 100 
grs. of leaves. 
Burgundy 3—3-50 applied June 6; tested June 17, 40 m. g. Cu per 100 
grs. of leaves. 
Bordeaux neutral applied June 6; tested June 17, 60 m. g. Cu per 100 
grs. of leaves. 
Lime sulphur applied June 4; tested June 17, showed no trace of sulphur 
remaining on any parts of the foliage. 
It will be seen that the copper-precipitate sprays adhere very well; but 
aside from this no conclusions as to their relative adherence are possible 
at this time. 
The following extracts are taken from the field notes made 
following the third application, August 25, 1919: 
In the sprayed and unpruned plats the fruits are for the most part 
entirely free of canker at this time; there are a few cases, usually in the 
tops of the trees, where fruits have been badly whipped by nearby branches 
and where canker has then resulted severely. Such infections are white 
in color and apparently new; it would seem probable that they are a 
result of the typhoon on August 16 and 17. At present the Burgundy 
and neutral Bordeaux plats show up to the best advantage, but such a 
statement is only an opinion, and substantial results will be obtained only 
at fruiting time. The lime-sulphur results are decidedly not equal in 
value to the results from the copper sprays; there are three to five fruits 
under each tree in the lime-sulphur plat, that fell due to canker infection; 
and on each tree there is a number of fruits badly cankered. This is a 
decided contrast to the results on the Burgundy and Bordeaux plats, where 
a search has to be made to find an infected fruit. 
