UNITED STATES DEPARTMENT OF AGRICULTURE 



I BULLETIN No. 490 



flf* 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER. 



January 18, 1917 



A PRELIMINARY REPORT ON THE OCCURRENCE 

 OF WESTERN RED-ROT IN PINUS PONDEROSA. 



By W. H. LONG, 

 Forest Pathologist, Office of Investigations in Forest Pathology. 



CONTENTS. 



Introduction 



Description of western red-rot 



Development of western red-rot in the tree. . . 

 Comparison of western red-rot and true red- 

 rot 



Cause of western red-rot . . . 



Page. 

 1 

 1 



2 



3 

 3 



Entrance of western red-rot into living trees. 4 Summary 



External signs of western red-rot 



Areas examined for western red-rot 



Number and kind of trees examined 



Western red-rot in black jack and yellow pine. 



Western red-rot and the rotation for western 



yellow pine 



Page. 

 4 

 5 

 5 



7 



INTRODUCTION. 



In the national forests of Arizona and New Mexico a varying per- 

 centage of the trees of western yellow 7 pine (Finns ponderosa) is 

 affected by an undescribed heart-rot, known locally as red-heart, red- 

 rot, gray-rot, top-rot, and heart-rot. The amount of this rot present 

 varies materially with the exposure, slope, and soil on which the 

 yellow pine is growing, as well as with the age of the timber itself. 

 It is the main heart-rot found in western yellow pine in Arizona and 

 New Mexico and causes an annual loss of thousands of dollars. 



This heart-rot is here called " western red-rot " in order to dis- 

 tinguish it from the true red-heart or red-rot, a very similar heart- 

 rot common in many species of conifers throughout the world. 

 True red-rot or ring scale is caused by Trametes pini, while western 

 red-rot is produced by an entirely different fungus. 



DESCRIPTION OF WESTERN RED-ROT. 



CROSS-SECTIONAL VIEW. 



Western red-rot may show in the end of a freshly cut log any one 

 of the following stages: (1) An early stage, in which the heartwood 

 is firm but shows reddish to dark-brown discolored areas. Such 



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