THE ROTS OF WESTERN WHITE PINE. 
11 
Table I shows that for each type of site the rot percentage gradu- 
ally increases from the youngest to the oldest age class, reaching 18 
per cent in the bottom sites and 14.7 per cent on the slope sites. 
Comparing similar age classes of the two types of sites, the figures 
for rot percentage on the bottom sites run consistently higher than 
those of the slope sites. 
Table III. — Comparison of bottom and slope sites of different sale areas of 
icestem white pine, shouting the relation of rots to site, independent of age 
classes. 
Bottom sites. 
Sale area. 
Slope sites. 
Sale area. 
Plat 
No. 
Num- 
ber of 
trees 
(basis). 
Average 
age 
(years). 
Rot 
(per 
cent). 
Plat 
No. 
Num- 
ber o.f 
tree's 
(basis). 
Average 
age 
(years). 
Rot 
(per 
cent). 
2 
1 
3 
1 
15 
18 
70 
347 
120 
379.1 
146.4 
72.0 
111.0 
159.6 
20.53 
8.01 
.002 
5.23 
9.32 
Bennett-Miner 
1 
1 
2 
la 
4 
71 
100 
149 
16 
33 
241 
340.6 
142.2 
79.0 
122.0 
118.0 
120.7 
14.62 
2.98 
/Silver Creek 
.63 
Do 
do 
Tent Creek 
.70 
2.19 
Total 
Total 
570 
712 
In comparing the average volume of rot for the two types of site 
in Table I a striking contrast is found between the butt-rot volumes. 
The average butt-rot volume on the bottom sites is found to greatly 
exceed the average volume for the slope sites, the average volume of 
trunk-rot is approximately equal, while the average volume of com- 
bined rots is shown to be somewhat larger on the bottom sites. 
INFECTION AGE. 
The average infection age, as defined in a previous work, 1 repre- 
sents the average age of the youngest trees in the stand open to first 
infection by fungous enemies. It is the average age at which the 
stand is most liable to first infection and below which infection 
rarely occurs. Subsequent to this age infection is to be guarded 
against, as the chances of infection, up to a certain point, will con- 
tinue to increase with the increase in age, number of injuries, etc. 
In this bulletin the term age of earliest infection is used in place 
of "average infection age." It is believed the newer term will more 
accurately convey the meaning intended. 
On the bottom sites, Table IV, the age of the earliest infection for 
the combined trunk and butt rots can be placed approximately in 
the 61 to 70 age class, since the first tree with visible decay is found 
in the 71 to 80 age class and is 73 years old. It must be remembered 
that actual infection is expected to take place some time before visible 
1 Weir, J. R., and Hubert, E. 
Dept. Agr. Bui. 722, 39 p., illus. 
E. A study of heart-rot in western hemlock. 
1918. 
TJ. S. 
