BLISTER-RUST OF WHITE PINE 
The blister-rust of five-needled pines and its alternate phase, the felt- 
rust of currants and gooseberries, has recently become an important 
disease in eastern United States. Previous to the importation of diseased 
white pine nursery-stock, this disease was confined to Europe. Recently 
it has assumed an epiphytotic character in several localities in northeastern 
United States. 
SYMPTOMS 
The symptoms produced by this disease will be studied in the order of 
their seasonal sequence on pine, currant and gooseberry. 
Blister-stage on pines. In the material and illustrations referred to, 
NOTE :— 
1. That the first evidence of the disease on the white pine is an 
indefinite, discolored canker-like area on the trunk or smaller branches. 
2. That in some cases a slight or marked hypertrophy of the 
bark occurs. (See Pl. Ind. Bur. Bul. 206, fig. 3, 4 and pl. I; or Farmers’ 
Bul. 742, fig. 3,5 and pl. 1.) DRaw or copy. 
: 3. That often a diseased tree may be detected by its stunted 
growth and bushy appearance. (See Farmers’ Bul. 742, fig. 1.) ‘ 
4. That the first external evidences of the pathogene are the 
minute light-yellow, bladder-like swellings which exude drops of liquid. 
These small pustules are pycnia (spermagonia) and within them are found 
minute spore-like bodies called pycnospores (spermatia). These spermatia 
are most generally believed to be non-functioning male gametes. They 
do not serve in any way to propagate the fungus. Usually the pycnial 
stage is formed several months after infection and during the autumn just 
previous to the production of aecia. 
5. The large hemispherical or pustular bladdery aecia pushed 
out from cracks in the invaded bark. Draw. : 
6. The aecia, at first yellow and enclosed by a papery peridium; 
later irregularly ruptured, allowing the yellow powdery contents to es- 
cape,—the aeciospores. The aecia are produced in early spring two or 
more years after infection. : 
7. The pock-like depressions in the bark where aecia have been 
borne. These characteristic markings on the cankered area constitute a 
reliable means of identification of diseased trees at any time of the year 
after the first crop of aecia has been produced. pDRaw. 
Summer stage on currants and gooseberries. Examine the diseased 
leaves of the different species of Ribes provided. oBSERVE:— 
8. That in the case of certain species definite leaf-spot lesions 
are produced; in others the fruit-bodies of the pathogene alone constitute 
the first signs of the disease. DRaw. 
9. The very small hemispherical pustules,—the uredinia, in 
groups on the under sides of the leaves. They are at first covered by the 
epidermis and are different in color from the remainder of the leaf, being 
slightly lighter green. DRAW as seen with the hand-lens. 
10. That later the uredinia become more or less orange-yellow in 
color; the covering (composed of leaf-epidermis and peridium) is rup- 
tured allowing the rusty yellow contents,—the uredospores, to escape. 
190 
