46 AGRICULTURE OF MAINE. 



APPEARANCE. 



The most characteristic symptom of the disease on the pines 

 is the irregular sweUings of the bark. A healthy pine usually 

 has practically uniform diameter throughout the length of each 

 year's growth. These swellings usually develop at the base 

 of the tree, or just at the lower branches, if it is a small tree. 

 If it is a large tree that is diseased, the smaller branches are 

 apt to show similar irregular swellings. Trees four or rive 

 years of age are usually stunted in their growth and have an 

 abnormal and compact appearance. Diseased trunks, limbs and 

 twigs affected with the fungus, finally die from its girding 

 effect and are very noticeable on inspection, as they remain 

 upright instead of drooping, as is the case with twigs affected 

 with frost or insects. The work of this disease is often con- 

 fused with that of the White Pine Weevil, which is becoming 

 numerous on our younger pines. This weevil, usually, kills 

 only the top central shoot, while the Blister Rust nearly always 

 kills side branches, or the upper part of the entire top. 



It is during May and June that the fruiting bodies appear 

 on the trees and it is at this time that the disease is usually 

 easie-st to determine. At first, these fruiting bodies appear in 

 the form of whitish blisters which are usually longer than 

 wide, and about the size of a small kernel of corn. These are 

 found at irregular intervals in the swollen portion of the bark. 

 After a few days the outer membrane, which is white in color, 

 breaks open and the top falls off, leaving dusty, bright yellow 

 spores exposed. These are blown out of their cup-like cavities 

 to neighboring currants and gooseberries. 



On currants and gooseberries the parasite attacks only the 

 under sides of the leaves. It has two distinct forms here. One 

 of these forms is known as the repeating stage, which is usually 

 throughout the summer season. Spores are formed that spread 

 to infect other currants and gooseberries, sometimes traveling 

 as far as four or five hundred yards and possibly even farther. 

 The other stage of the disease, on the currants and gooseber- 

 ries, is in the fall when a different form of spores appears on 

 some part of the leaves, where the repeating stage is produced. 

 These spores cannot spread the disease to other currants and 

 gooseberries, but only germinate upon neighboring pines. The 

 spore produced by the disease upon the pines cannot produce 



