422 The Philippine Journal of Science 1921 
gle are severely attacked in both regions. The Nakorn Chaisri 
seedless pummelo is extremely delicate and, consequently, most 
apt to be severely attacked by canker and other diseases. An ex- 
tensive study of the several varieties may show some slight resist- 
ance, but in general all trees of this type are attacked. Fruit 
rots may take place while in storage, especially on fruits that 
have been injured during picking and handling. This trouble 
can, however, be entirely avoided by proper handling and ship- 
ping. In order to obtain the highest possible yield of unmarred 
fruits of this variety, the best of culture and care will have to 
be exercised. If this be done, it will be possible to produce the 
Nakorn Chaisri pummelo commercially. An intensive study of 
this type should be undertaken to determine whether or not a 
more resistant strain can be developed. 
The diseases listed below may be found on all varieties of 
pummelos. However, the susceptibility to disease of varieties 
in the different groups seems to vary. 
Algae ; parasitic ; undetermined. Parasitic algae may produce 
a leaf spotting which, however, is not serious. 
Aschersonia aleyrodis Webber. Scale insects on citrus trees 
may be attacked by Aschersonia aleyrodis Webb. It is a bene- 
ficial fungus as it reduces the number of coccids. Scale insects 
of various species, as later listed, may be severe on stem, leaves, 
and fruit. 
Bark rot ; Diplodia. A common bark rot caused by a Diplodia 
may attack the pummelo, but does not appear to be serious. 
The same fungus produces the gummosis of trees and the black, 
sooty fruit rot. 
Canker; Pseudomonas citri Hasse. On the Nakorn Chaisri 
seedless variety the canker is extremely serious, as it attacks 
leaf, stem, and fruit (Plate 15, fig. 2). There appears to be 
no individual variation as to susceptibility. Brownish, can- 
kered areas are produced on the affected parts. The growers 
do not consider the disease to be a serious one and believe that 
it is due to a caterpillar or to some other insect. If only a 
few cankered infections develop on the fruits, the planters say 
that the sale is not hindered; but if the affection is severe, the 
price obtained for such fruits is somewhat lower. The great 
demand, especially among the Chinese, for the best types of 
fruit and their comparative scarcity account for their ready 
sale even though defaced. The growers recognize the fact that 
a rot does not start from the cankered area. The canker ap- 
pears to be more prevalent in well-kept plantations where the 
