Apr. 1, 1925 
Relation of Weather to White Pine Blister Rust 
599 
quently in British Columbia, most of 
the oldest infections noted above were 
in places where they were absent. 
None were found at Thurston Bay and 
there was no evidence that any had 
ever been planted in that locality. 
The oldest infections at Bold Point 
were in a mountain ravine fully a mile 
from any black currants. This does 
not mean that the black currants were 
not susceptible to the rust, but rather 
that there was an abundance of sus¬ 
ceptible wild Ribes near the infected 
pines. As a matter of fact, these cul¬ 
tivated black currants apparently 
caused infection in pines near them in 
1917 and again in 1920 and 1921. At 
Shoal Bay the single old infection and 
two of more recent date evidently 
came from old cultivated black currants. 
It has been pointed out that there 
was little or no infection in British 
Columbia in 1914 or 1915 and very 
little in 1916. In 1917, however, there 
seems to have been a great deal and a 
much wider spread of the rust than in 
any previous year. It advanced to 
the east 60 miles as far as Agassiz, 40 
miles southeast to Blaine, Wash., 
north and west 150 miles practically to 
the limits of the white pine in the coast 
belt, and apparently eastward for at 
least 150 miles across the dry belt to 
Canoe, Revelstoke, and Beaton. 
The infections at Agassiz were upon 
the outer branches of 30-year-old 
Pinus strobus 7 near cultivated black 
currants. The infected pine near 
Blaine and in nearly all the other 
places in the Fraser Valley were found 
in the vicinity of cultivated black 
currants. 
Fourteen infections were found in 
1922 east of the dry belt, 7 at Canoe, 
1 at Revelstoke, and 6 at Beaton. They 
were apparently of the same age and 
were in the 1916 and 1917 internodes 
( 1 ). Of seven cankers examined by the 
writer, five were in the 1916 internode 
and two in 1917 internodes. They were 
apparently of the same age as those 
found in the 1915, 1916, and 1917 inter- 
nodes in the coast region. 
No infection was found south of 
Blaine, although much more intensive 
scouting was carried on in Washington 
than in British Columbia. A great deal 
of the scouting was done by men who 
worked both in Washington and in 
British Columbia. 
In 1918 and 1919 there was a little 
infection in the vicinity of the oldest 
cankers in the coast region. 7 8 In 1920 
there was considerable infection in the 
immediate vicinity of Ribes near 1917 
infections (see Table I). In 1921 there 
was a much heavier infection than in 
1920 (see Tables II, IV, and V). 
Very careful search was made during 
the summer of 1923 in the interior of 
British Columbia, particularly at 
Canoe, Revelstoke, and Beaton, to find 
and destroy all pine infections. Of 
these 88 are shown in Table VIII. 
Table VIII.— Distribution of 88 pine 
infections found at Canoe , Revelstoke , 
and Beaton , B. C., during the summer 
of 1923 
Number of infections at— 
Intern ode of— 
Canoe 
Revel¬ 
stoke 
Beaton 
1917_ 
4 
5 
1 
1918_ 
3 
11 
1 
1919_ 
1 
9 
9 
1920_ 
6 
14 
10 
1921 
6 
8 
In addition to the 88 infections men¬ 
tioned in Table VIII, 10 were later 
reported by Davidson ( 2 ). These with 
the 14 found in 1922 and the 1 at 
Nakusp make a total of 113 for the 
four centers east of the dry belt. 
These apparently represented three 
stages in the development of the dis¬ 
ease, incipient infections, cankers of 
one year, and those which had pro¬ 
duced aecia for three or four years. 
This is a very small number upon 
which to determine the exact years of 
infection. It has been suggested that 
the original infection occurred in 1918. 
From the age of the cankers, however, 
and their distribution in the branches 
and stems it seems more probable that 
infection first occurred in three of the 
localities in 1917, and that later infec¬ 
tion occurred in 1920 and 1921. The 
single infection found at Nakusp was 
in the internode of 1919 or 1920. This 
could not have occurred earlier than 
1919, and since it produced aecia in 
1923, it probably did not occur later 
than 1920. 
7 These trees were brought from Ontario in about 1894 or 1895. No evidence was found to indicate that 
any of them were infected before 1917. 
8 One infection at least occurred in either 1919 orl920 at Nakusp, in the Columbia Valley. 
