22 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. 



In some localities a rust {Peridermium montanum) attacks the 

 leaves of lodgepole, causing them to fall prematurely. Another rust 

 (Peridermium harknessii) attacks loclgepole in western Montana, 

 causing galls to form on the trunk and branches, which stunts and 

 sometimes kills the tree. 



One of the false mistletoes (Basoumfskya americana) is often 

 found on lodgepole, but does little serious damage except in certain 

 localities, where it may greatly affect the growth of the tree. It 

 usually attacks young stands, and in dense ones most of the trees may 

 be infested. Mistletoe causes an abnormal growth at the point of 

 attack, which on side branches forms a compact, bushy mass of 

 twigs commonly called " witch's broom." In small trees infested 

 stems or branches are sometimes swollen to twice their natural 

 diameter. 



SMELTER FUMES. 



The Washoe smelter at Anaconda, just outside of the boundary of 

 the Deerlodge National Forest, is the largest copper smelter in the 

 world, handling approximately 10,000 tons of ore daily and pro- 

 ducing 25 per cent of the copper output of the United States. Chem- 

 ists have estimated that at least 2,500 tons of sulphur dioxide and at 

 least 25 tons of arsenic trioxide are daily thrown into the atmosphere 

 from the top of the stack. The arsenic does not damage the timber, 

 but when deposited on the forage is injurious and sometimes fatal 

 to grazing animals. Sulphur dioxide is injurious to vegetation in 

 general. Experiments have shown that as little as one part of sul- 

 phur dioxide with a million parts of air will kill pine seedlings when 

 the trees are exposed for any length of time. Even at a distance of 

 many miles from Anaconda the air in the smoke stream may contain 

 as many as 80 parts of sulphur dioxide to a million parts of air. At 

 a distance of 10 miles from the smelter the sulphur is often so strong 

 as to cause persons to cough. 



Sulphur dioxide injures trees by destroying the chlorophyll in the 

 leaves, which first turn yellow and later red-brown. The damage 

 usually extends over several years, especially if the trees are at some 

 distance from the smelter. At first only the weaker leaves are killed, 

 but later the younger ones succumb to repeated baths in the smoke 

 stream. Three stages in the defoliation of trees by smelter fumes 

 have been recognized. The first is when the older leaves die and fall 

 prematurely, the tree still retaining a considerable amount of foliage 

 and the appearance of health. In the second stage the foliage be- 

 comes decidedly thin, and in the last or acute one only the needles 

 of the current year are left green on the tree. (Plate V, fig. 1.) 

 These latter are usually badly damaged or killed during the winter, 

 and the tree may fail to put forth fresh leaves in the spring. In 

 some cases, however, the acute stage lasts for several years. The an- 



