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WORK ON THE WHITE PINE BLISTER RUST IN 
MINNESOTA, 1916. 
His Excellency, 
J. A. A. BURNgUIST. 
Dear Sir : As you are aware the State of Minnesota is unexpect- 
edly threatened hy a plant disease, which is a menace, not only to the 
white pine timber now standing, but also to the cause of reforestation, 
upon which we place so much dependence for our future w^elfare, as 
^well as to all five leaf pines used for ornamental purposes in various 
parts of the state, particularly upon the estates in the neighborhood of 
our towns and cities. Another aspect in which we must view this 
unexpected infestation is that concerned with the nursery business and 
allied interests, since should this disease become widespread, a quaran- 
tine might be imposed upon all exports of certain shrubs and trees. 
The disease referred to is known as the White Pine Blister Rust 
(Croiiartiiini ribicola Fischer or Pcridcnniiim strobi Klcb.) This is a 
fungus parasite with two separate and distinct hosts, the white pine 
primarily and other five-leaf pines, limber pine (P. dcxilis), stone pine 
(P. cembra), both found in varying abundance in Minnesota nurseries, 
and used thruout the state as ornamentals, as well as al)out seven other 
varieties occurring in various parts of America. The other host upon 
which it is found during the summer months is the genus Ribcs, con- 
taining as now constituted, both currants and gooseberries, wild and 
cultivated. Details of this relationship in the life history of the fungus 
are given below. The disease is of European origin, and was imported 
into this country on pine seedlings as early as 1900 or earlier. In 1909 
large numbers of these were l^rought to America. (LT. S. Dept, of Agr. 
Farmers’ Bulletin 7-12, Spalding. ) The original home of tins rust is 
said to 1:>e Eastern Asia or Serbia, spreading thence to England and 
northern and central Europe. The principal infestations in this coun- 
try evidently came from Germany. 
The foreign seedlings referred to above were widely distributed be- 
fore it was known that they were diseased; New York, Pennsylvania, 
Connecticut, New Hampshire, Vermont, Massachusetts, as well as Ohio 
and Indiana received trees of this sort and in these states the rust 
EXPLANATION OF PLATE I. 
A. Diseased white pine with Ijlisters broken open, spreading the disease to any rnrrants or 
goosel)erries in the vicinity. 
I>. Early summer stage on lower surface of currant leaves, repeating on currant leaves or 
gooseberry leaves during the rest of the season, and a new crop of spores apj)earing 
every two weeks. 
C. Early summer stage much magnified. 
D. Late summer and fall stage on lower surface of a currant spreading the disease hack to 
neighboring pines. Courtesy of Bureau of Plant Industry, LT. S. Dep. of Agriculture. 
