146 The Philippine Journal of Science 1922 
Upon the foliage of the Washington navel, citrus canker 
must effect some reduction in the amount of leaf surface capable 
of functioning. An estimate of such injury is of course dif- 
ficult but, to offer a comparison, it is somewhat similar to the 
effect of shot-hole disease of the apricot, or such similar leaf- 
spot diseases on the apple or the pear. Citrus canker, moreover, 
must shorten to some extent the life of an affected leaf, for 
such affected leaves are the first to drop on the occurrence of 
any slight stimulus, as a brisk shower or a strong spray appli- 
cation (see Plate 2, fig. 1). 
The losses due to citrus canker upon the Washington navel, 
which would be most appreciated by the growers, are due to 
infections upon the fruits. A dropping of the fruits, infected 
while they were small, was observed upon the formalin plat 
and the untreated plats of these experiments. This is rather 
poorly shown in the photograph in Plate 2, fig. 2. This dropping 
of the fruits did not occur upon the treated plats lying adjacent, 
so that it is reasonable to assume that this fruit drop was due 
to the canker infections, and not to drought or other nutrition 
causes. The fruit drop due to canker was not sufficiently exten- 
sive to be appreciated by the commercial growers. 
Secondly, the fruits if infected when larger, although they 
do not fall, are more or less blemished. In Japan this is not 
a serious handicap. In fact, infected fruits matured earlier 
than uninfected fruits, and the orchard coolies in selecting 
oranges for eating would choose those badly cankered, stating 
that they were sweeter. 
In the United States, however, where marketing is consider- 
ably more advanced, the blemish due to canker would presumably 
necessitate lower prices for infected fruits. It is very difficult 
to state such losses except possibly by comparison. The blemish 
due to canker would be similar to peach scab or pear scab, but 
probably more abundant. Table 8 shows that blemished fruits 
due to citrus canker amounted to from 80 to 96 per cent upon 
untreated plats; this is of course a serious proportion. Such 
blemishes are shown in Plate 3, and an idea of the effect of these 
fruits in the market can be best obtained by those more familiar 
with market conditions. 
Another loss, very difficult to appreciate, but fortunately 
apparent from the present experimental results, is due to 4 
reduction in weight of fruits affected with canker. This is shown 
. in Table 14. oe 
This table shows an average loss in weight obtained from 
40,523 fruits, of 0.2 gram per cankered fruit. This amount 
