UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 490 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



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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. 



Page. 



Introduction 1 



Description of western red-rot 1 



Development of western red-rot in the tree. . . 2 

 Comparison of western red-rot and true red- 

 rot 3 



Cause of western red-rot 3 



Entrance of western red-rot into living trees. 4 



Page. 



External signs of western red-rot 4 



Areas examined for western red-rot 5 



Number and kind of trees examined 5 



Western red-rot in black jack and yellow pine. 7 

 Western red-rot and the rotation for western 



yellow pine 7 



Summary f .. . 8. 



INTRODUCTION. 



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

 centage of the trees of western yellow pine (Pinus 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 pint, 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 vhich the heartwood 

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



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