402 THALLOPHYTES 
disease on the leaves and fruit. Upon the Apple tree, the aecidia 
stage 1s produced, and the aecidiospores are able to attack the 
Cedar and form new galls, thus completing the life cycle as shown 
in Figure 361. ; 
Pine Tree Blister-rust (Cronartium ribicola). — As its name 
suggests this Rust attacks Pine trees. It was introduced from 
Europe about ten years ago 
and has now become a seri- 
ous disease in this country. 
It has its aecidial stage on 
Pines with five leaves in a 
fascicle, such as the White 
Pine and Sugar Pine, and 
has species of Ribes (Goose- 
berries and Currants) as the 
other host. In this Rust the 
aecidial stage is the most de- 
structive. The mycelium of 
the aecidial stage kills the 
cambium and inner bark of 
Pines, thus causing the 
death of branches and some- 
al ~ times of the entire tree. 
Fie. 360.— A Cedar Apple which has Both uredospores and teleu- 
developed the gelatinous branches con- tospores are produced on 
taining numerous teleutospores. The 
teleutospores produce sporidia or basidio- the infected Currant and 
spores that attack the Apple tree. These Gooseberry bushes, which 
gelatinous branches develop in the spring are apparently very little 
after a rain and while the leaves and injured thereby. Pines are 
shoots of the Apple are young and easily - A 
attacked. After Bulletin 257, Wisconsin infected through the basid- 
Aer. Exp. Sta. iospores. The chief means 
of checking the spread of 
the disease is through the destruction of the wild Currant and 
Gooseberry bushes. 
The damage done to Pine trees is serious and since our 
Pine forests are valued at many millions of dollars, it is 
not surprising that our government has put restrictions 
upon the importation of Pines from Europe and has appro- 
priated large sums of money to be expended in checking 
this disease. 
pins ekcaee 
_- 3 ten. 
