B. P. I. 46. V. P. P. I. 100. 



m HE " BLUING" AND THE "RED ROT" OF THE WEST- 

 ERN YELLOW PINE, WITH SPECIAL REFERENCE TO 

 THE BLACK HILLS FOREST RESERVE. 



INTRODUCTION. 



The present investigation was undertaken to determine 



(1) The cause of the blue color of the dead wood of the western 

 yellow pine, commonly known as the bull pine (Pinus ponderosd), and 

 the effect of the coloring on the value of the wood. 



(2) The reason for the subsequent decay of the wood, the rate of 

 decay, and whether the decay could be prevented. 



(3) Whether it would be possible to use the dead wood before it 

 decayed; first, to reduce the fire danger; second, to prevent the decay 

 and thereby save an immense quantity of timber. 



DEATH OF THE TREES. 



The physiological changes which take place in the bull pine (Pinus 

 ponderosa) as a result of the attack of the pine-bark beetle (Dendroc- 

 tonus ponderosse Hopk/') are intimately connected with the fungus 

 diseases under consideration, and may therefore be referred to briefty. 



According to Hopkins, the beetles enter the bark of the living trees 

 in July, August, and September. The primary longitudinal burrows or 

 galleries are excavated by the adult beetles, and the transverse, broad, 

 or larval mines (Bull. 32, n. s., Division of Entomology, U. S. Depart- 

 ment of Agriculture, Pis. I and III and fig. 1) through the inner bark 

 and cambium of the main trunk have the effect of completely girdling 

 the tree, and by September the cambium and the bark on the lower 

 portion of the trunk are dead. The foliage of the trees thus attacked, 

 however, shows no change from the normal healthy green until the 

 following spring, when the leaves begin to fade. 



The first signs of disease noticeable in an affected tree are visible in 

 the spring of the year following that of the attack by the beetle. Here 



a Hopkins, A. D. Insect Enemies of the Pine in the Black Hills Forest Reserve. 

 Bull. 32, n. s., Division of Entomology, U. S. Dept. of Agriculture, pp. 9, 10. 



9 



