144 
The Philippine Journal of Science 
1921 
Table 8 shows that in this plat canker, even though untreated, 
decreased to some extent from what it was at the beginning of 
the experiment. Although there are possible explanations for 
this they will not be entered into in detail here; granted that 
seasonal differences permitted some reduction in canker, it is 
apparent that considerably more reduction was obtained on 
the sprayed plats. 
PLAT VI, AT LOS BANOS 
It was intended to run this plat entirely as a test of formalin 
against citrus canker. It became evident a few weeks after 
the first application, however, that new infections were appear- 
ing and that applications of formalin as a preventive would be 
necessary much too often to be feasible. The spraying with 
formalin solution was therefore abandoned as a preventive but 
was subsequently used on other plats for clean-up work. 
DISCUSSION OF RESULTS AT LOS BANOS 
The comparative value of the sprays which were tried is 
briefly summarized as follows: Cankers recurred after the ap- 
plication of formalin 1 to 100 without any reduction in number 
or distribution; the results at Los Banos are therefore taken 
to indicate that formalin has little value as a preventive spray. 
In the heavy tropical rains in the Philippines lime sulphur did 
not adhere well to the foliage, although it is possible that in 
regions of more moderate rainfall lime sulphur would be of 
great value. Burgundy and Bordeaux mixtures, when freshly 
prepared, adhered to the foliage very well and no difficulty was 
experienced with the washing of such copper sprays from the 
foliage. The determination of the length of the periods between 
spraying depended, therefore, chiefly upon the amount of new 
growth which came out and was unprotected by coatings of spray. 
As to the comparative merits of Burgundy and Bordeaux mix- 
tures as preventives, little or no difference showed in the results. 
From Tables 6 and 7, showing the results of plats sprayed 
with Burgundy and Bordeaux mixtures, it is apparent that the 
amounts of citrus canker in most cases were reduced to some 
extent; Table 5, showing an untreated plat, shows no decrease 
in canker; Table 8, also untreated, destroys some of the value 
of the results on the treated plats, since it also in some cases 
shows a decrease in the amount of canker affection. There’ 
are possible explanations for this ; but, regardless of such expla- 
nations, it is apparent that the reduction in the amounts of 
canker in the treated plats is greater than in either of the 
untreated plats. 
