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Author Topic: Orange Mold  (Read 46086 times)

Offline PhilM

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Orange Mold
« on: March 25, 2015, 11:46:26 AM »
QUESTION from the industry: Please see the photos. From what I have read this is Fusiform Rust, supposedly, through its growth cycle it is transferred from oaks, to pine, and back to oak.  The descriptions I have read all discuss this while it is still om the Pine, weather it is on the trunk, which seems to cause the most damage, and branches.  I am seeing an alarming amount come in on our KD19 "2 X" Pine, it sometimes there on delivery, and if we have rain or high humidity it gets out of control.  Now, it seems there is no solution, which I find difficult to believe, what worries me the most is, in the south, the Southern yellow Pine is of great importance in many aspects of our society. 

I have just read an article that states a blistering rust type mold/fungus has virtually rendered the White Pine of northwest United States and/or Canada a non-viable source in regards to any commercial uses.
Could this happen here, to Southern Yellow Pine?  And why does it seem there is no one who seems overly concerned of the potential loss of this tree, as it is grown, harvested, processed and sold for various end uses  in our region.  There are some states that have laws against harvesting and transporting this type infestation in an effort to have strong forests in the future.  I am unaware of any at this time.

ANSWER from Phil Mitchell Ph.D.: The orange mold shown in some photos is a surface mold that can grow on green lumber, air dried lumber, or even kiln dried lumber that is stored in warm and very humid conditions.  This fungus penetrates the sapwood, but discoloration is limited to the surface of softwoods.  Mold fungi do not rot the wood and have little effect on strength.  Some photographs show blue stain fungi which is a sap stain fungi.  Blue stain fungi do not rot the wood and have little effect on strength except that they may reduce toughness or shock resistance.  One photo shows what appears to be cotton between pieces.  These are actual fungal hyphae strands growing on the lumber surface in profusion.  I have seen this form quickly (within 24 hours after sawing and stacking) in the mid-south if drying is delayed during hot humid weather. 

The best prevention against these stain fungi and surface molds is to quickly process cut logs into lumber and get the lumber up on sticks and in the kiln.  Sometimes dip treatments are used to retard the development of surface stain, but such treatments cannot prevent stain developing on the interior of the piece.

Fusiform rust is a disease of living trees and as such does not attack lumber.  Control of fusiform rust is best accomplished by silivicultural treatments in the forests although fungicides can more practically be applied in nurseries.  A good web site from the Forest Service discusses these aspects of control:
« Last Edit: March 25, 2015, 11:53:49 AM by admin »



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