THE WHITE-PINE BLISTER RUST. 9 



Aside from the regions occupied by the four previously mentioned 

 species of white pines, we have the entire remainder of the country 

 in which these species, as well as any other of the white pines, both 

 foreign and American, may be planted as ornamentals. Hence, if 

 the Northeastern States, which do a large proportion of the orna- 

 mental nursery-stock trade of the country, become thoroughly 

 infected by this disease, as is sure to happen very shortly if the State 

 authorities are not given complete legal authority for any necessary 

 measures to control it, there is good reason to expect the white-pine 

 blister rust to reach practically all parts of the country where any 

 of the 5-needle pines will grow. 



APPEARANCE OF THE DISEASE. 



Upon pines the most characteristic symptom is the presence of 

 irregular swellings in the bark. A healthy white pine has a prac- 

 tically uniform diameter throughout the length of each year's growth. 

 A pine affected with this disease is apt to develop a marked swelling 

 at the lower branches if it is a small tree (fig. 5). If a large tree is 

 affected, the smaller branches are apt to show similar more or less 

 irregular swellings. These commonly extend to the bases of smaller 

 side branches and sometimes out into those branches (fig. 5). Some- 

 times this swelling, instead of showing as a gradually tapering swell- 

 ing, is very irregular, the bark having a peculiar distended appearance, 

 with rounded swellings located at leaf scars, that is, where a bundle 

 of needles has fallen from the twig (fig. 3). Upon trees only 3 or 4 

 years of age the disease may cause a shortening of growth and a 

 dwarfing of the top, so that it has an abnormally compact appearance 

 (fig. 1). Upon branches of larger trees this is not usually very 

 evident. Occasionally the leaves upon the affected part of the branch 

 or stem become yellowish, but this is not common. The diseased 

 trunks, branches, or twigs finally die from the girdling effect of the 

 fungus and thus become very noticeable, as they remain upright 

 and do not droop as do twigs affected by frost or by certain insects. 

 Trees up to 25 years of age may have the tops killed in the same way. 

 Do not confuse such dead branches with the work of the white-pine 

 weevil, which is common in many localities. The weevil usually 

 kills only the top central shoot down to the uppermost branches, 

 while the blister rust usually kills side branches or the upper part of 

 the entire top of the tree. 



The most certain symptom, however, is that furnished by the 

 fruiting bodies of the parasite, which form upon the thickened bark 

 in the spring from the latter part of April until the middle of June, 

 depending upon the locality and the weather conditions. At first, 

 these thrust themselves from within outward through the swollen 

 bark, in the form of whitish blisters as large as a child's finger nail. 



