122 The Philippine Journal of Science 1922 
so susceptible to canker as to be very difficult of control; the 
control of citrus canker on such hosts was not economically 
feasible in humid climates, by the methods employed. Control 
had been effected upon the class of citrus varieties of the general 
susceptibility of the East Indian pummelo (Citrus maxima), 
Washington navel orange (Citrus sinensis), and other sweet 
oranges of Florida origin; however, the feasibility of control 
from a commercial viewpoint was undetermined. A class of 
varieties that showed still less susceptibility consisted of the 
sweet oranges of the Mediterranean group (Citrus sinensis), 
such as the Jaffa, Du Roi, Mediterranean Sweet; some of the 
American-grown lemon varieties (Citrus limonia), the Tahiti 
lime (Citrus aurantifolia), and the Unshiu (Satsuma) orange 
varieties (Citrus nobilis var. unshiu). In the Philippines control 
on such varieties was so readily obtained that its commercial 
feasibility seemed very probable. The calamondin (Citrus 
mitis), the mandarin orange (Citrus nobilis var. deliciosa), the 
round kumquat (Fortunella japonica), and some of the citrons 
(Citrus medica) constituted a class of citrus varieties of such 
slight susceptibility to canker that control measures upon them 
were unnecessary. 
It seemed desirable to try further control measures on an 
orchard planted exclusively to a variety of the same degree of 
susceptibility as the Washington navel; this class contains many 
of the commercially grown varieties, and it seemed important 
to determine the feasibility of such measures from a standpoint 
of costs on such a class of hosts. Such further experiments 
were, therefore, undertaken in an orchard of the Washington 
navel variety at Saigomura, Nagasaki Prefecture, on Kyushiu 
Island in southern Japan. 
CLIMATIC CONDITIONS IN NAGASAKI PREFECTURE 
Temperature, humidity, rainfall, and wind velocity and direc- 
tion were recorded at the orchard during the actual operations 
of the experiment. However, to obtain a proper idea of the 
seasonal conditions, extracts will be presented here from weather 
data for a five-year period, collected by the Nagasaki Agricultural 
Experiment Station. The temperature data are shown first, in 
Table 1. 
From Table 1 it can be seen that there is a winter season from 
early November until the end of April, during which the temper- 
atures are, with a few exceptions, below 20°C. Although the 
minimum temperature for the growth of the canker organism 
