NOTE ON WESTERN RED ROT IN PINUS 
PONDEROSA 
W. H. Long 
In the National Forests of Arizona and New Mexico, a vary- 
ing percentage of the trees of western yellow pine {Finns pon- 
derosa) is affected by a 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. 
This heart-rot is called in this paper “ western red rot ” in order 
to distinguish it from the true “ red heart ” or “ red rot,” a very 
similar heart-rot common in many species of conifers. True 
“red rot” or “ring scale” is caused by Trametes pini, while 
“ western red rot ” is produced by an entirely different fungus. 
Western red rot has three stages in its development; (i) An 
initial stage in which the affected heartwood is firm but shows 
reddish to dark brown discolored areas; (2) an intermediate 
stage in which the diseased heartwood is whitish or gray in color 
and is more or less delignified; and (3) a final stage in which 
much of the heartwood has disappeared due to the absorption of 
the delignified portions, while the wood particles left are brittle 
and easily crumble when handled. 
The fungus which causes “ western red rot ” never forms brown, 
woody, perennial fruiting bodies on the boles of living affected 
pine trees as Trametes pini does, but forms annual fruiting bodies 
which usually develop as white encrusting layers on the underside 
of logs. However, fruiting bodies have been found which have 
distinct and well-formed pilei. The pileate form of the fungus 
resembles very closely Polyporus Ellisianus {Tyromyces Ellisi- 
anns of Murrill in North American Flora) and is probably this 
species. 
t 
178 
