188 REPORT OF THE BOTANICAL DEPARTMENT OF THE 
AN OUTBREAK OF THE —EUROPMAg! 
CURRANT RUST.1# 
(Cronartium ribicola Dietr.) 

TT 
Se oe Vy cae 
SUMMARY. 
In September, 1906, the Station currant plantation was found to 
be abundantly infested with Cronartium ribicola, a European rust 
fungus hitherto unknown to America. It appeared in the form of a 
conspicuous orange-colored powder on the under surface of the 
leaves. Of 54 varieties representing three species of Ribes (R. 
nigrum, R. rubrum and R. aureum) 48 were more or less affected. 
It was also found on &. grossularia and R. wrriguum. With the 
exception of a single affected leaf in a plantation one-half mile west 
of the Station it was not found outside the Station grounds. 
In Europe this rust has been known for fifty years and is widely 
distributed. As a currant disease it is unimportant. ‘he chief 
danger from it lies in its effect on white pines. In one of its stages 
(eecidium) the fungus attacks the trunk and branches of the white 
pine causing a serious disease called blister rust. Its introduction 
into America is to regretted. Doubtless it is a recent importation 
from Europe, but just how it came onto the Station grounds is not 
known. The only white pines in the immediate vicinity of the 
affected plantation are two small trees 125 feet west, planted eight 
years ago. Possibly these trees are the source of infection. 
Remedial measures consist, chiefly, in the removal of whichever 
host (pines or currants) is regarded as of least value. In order to 
stamp out the disease, if possible, all plants of the genus Ribes on 
the Station grounds have been destroyed. 
* Read in abstract, Dec. 20, 1906, before Section G of the American Assoc- 
ciation for the Advancement of Science at the fifty-sixth annual meeting, 
held in New York. 
*Reprint of Technical Bulletin No. 2. 
