June 21,1924 
Survey of Blister Bust Infection of Pines 
1257 
SEVERITY OF BLISTER RUST INFECTION IN DIFFERENT CROWN CLASSES 
PERCENTAGE OF PINES INFECTED BY CROWN CLASSES 
intermediate 
DOMINANT 
WR CENT INFECTED # * ia jV so §# 7 * ' *0 90 too 
Fig. 4.—A compilation of data for all trees on thirty-two A-acre plots located 100 to 400 feet from the site of 
the imported black currants in the west half of the area shown in fig. 1 
CONDITION OF THE STAND 
As shown in figure 5, there has been a constant increase in the number of trees 
dying from the effect of blister rust, while the number of infected trees has remained 
the same as in 1917. The number of healthy trees has been augmented by 485 
young pines which seeded in during the four-year control period. This demon¬ 
strates that the destruction of Ribes prevented the occurrence of new infections 
and allowed pine reproduction to continue at an average annual rate of 60 trees 
per acre. 
CONDITION OF STAND ON CONTROL AREA IN 1917 AND 1921 
A ni7 
Mil 
-MCPWWMWar «w/ mr 
mopaot* a/ rmso « 
/ta* 1490 /MO 
iooo atoo i*oo 
Fig. 5.—A compilation of data collected on the thirty-two A-acre plots described under fig. 4 
SUMMARY 
Investigations reported in this paper indicate that a patch of cultivated black 
currant plants introduced from England in 1897 and planted at Kittery Point, 
Me., during the same year, established a primary infection center of the white- 
pine blister rust whence the disease became widely spread through the neighbor¬ 
ing white-pine forests. On the basis of detailed investigations conducted on 
experimental areas selected in and about the primary infection center, the 
following facts are evidenced: 
1. Cultivated black currants were the Ribes mainly responsible for causing 
the pine infection on the area studied. 
2. In cases where either wild or cultivated Ribes bushes had caused pine 
infection, the greatest amount of infection occurred in the nearest pine stands, 
and the infection from these bushes rapidly decreased at greater distances. 
3. The highest degrees of pine infection were in the paths of late summer 
and autumn storm winds. 
