80 BUKLETIX 957, U. S. DEPARTMENT OE AGRICULTURE. 
Fungi which parasitize Cronartium ribicola are not uncommon. 
Their use in artificial inoculation of infections on pines has been 
attempted ^ 172. 173. 174). but with little success. There appears 
to be little prospect for success commensurate with the expense 
involved. 
The separation of the pines from the Ribes plants is the most 
efficient method of controlling the disease in a given locality. To 
judge from the frequency of this recommendation for combating 
the disease in European literature, apparently considerable work of 
this kind has been done in Europe: but no definite statement of 
results in specific instances have been found. 
The use of screens of another species of tree between Ribes and 
Pinus strobus has been recommended in Europe (131. p. 41). Xo 
one has stated the results of such treatment in any given instance, 
however. 
There must be a chance to secure much valuable data on the 
success or failure of various methods of treatment which have been 
tested in Europe, but which have never been published. This can 
only be done by making definite investigations in Europe from the 
American standpoint. It must be remembered that from the 
European point of view the white pine is an introduced and com- 
paratively unimportant tree. Its diseases, therefore, are not made 
the subject of systematic and prolonged study. Many facts of value 
fundamental to the control of this disease in America can only be 
determined by the intimate study on the ground of the much older 
infections of Europe. 
Experiments in Control in North America. 
In all control of parasitic plant diseases the fundamental thing is 
to determine the extent and the distribution of the disease to be 
controlled. The parasitic fungi are so generally distributed by the 
wind and are so insidious in their spread that they usually have 
gotten well started before then presence is discovered. Xewly dis- 
covered imported diseases must be attacked at once or not at all, 
if eradication is to be accomplished, but more attention should be 
given to the matter of deterniining reliably the extent of outbreaks 
of such diseases. Scouting is a very important part of any disease 
eradication or control campaign. A well-conducted, intensive, 
plant-disease survey will do much to aid in determining the status 
of a new disease. 
METHODS USED. 
The control of white-pine blister rust has been attempted in 
Xorth America (1) by means of quarantines of the host plants. 
(2) by the eradication of advance infections. 3 by the separation 
of the two hosts. (4) bv sanitation. (5) bv screening Ribes or pines 
