Wood Deterioration and its Prevention

1. Wood Deterioration and its Prevention

7. Wood Losses 10 % of all wood cut in the U.S. replaces wood that has failed in service

8. Biotic vs Abiotic • Abiotic: Non-living agents • Heat: (>150 F)(Fire) hemicellulose>cellulose>lignin • Chemicals: Strong bases, strong acids, salts • Mechanical: impacts, erosion • Sunlight: UV weathering attacks lignin

13. Biotic Agents • Fungi • Insects • Woodpeckers • Marine borers

14. Water Oxygen (air) Temperature Food

15. Biotic Requirements • Water (>20% MC but really 30 % or the fsp) • Moderate Temperature (32° to 100°F) • Oxygen • Food

16. Where is the Water in Wood? • Occurs in two locations: • Within cell lumen • Liquid • Called free water • Within the cell wall • Captured in cell wall matrix • Called bound water Liquid Free Water Cell Wall with Bound Water Wood & Water

17. Free Water • Free water is liquid water that fills wood’s void spaces and affects only • Thermal conductivity • Mass Free Water Wood & Water

18. From Haygreen & Bowyer (1989) Equilibrium Moisture Content The Equilibrium Moisture Content (EMC) is the MC of wood when it is in equilibrium with the environment’s temperature and humidity. Wood & Water

19. Temperature & Humidity EMC of wood at various temperature and humidity values Wood & Water

21. Bacteria • Remove pit membranes • Degrade extractives • Digest cell walls (Tunneling) • Can be important in submerged wood

22. Fungi

23. Fungal Spores are Everywhere

24. Fungal Types • Molds/Stain Fungi • Soft rot fungi • Brown rot fungi • White rot fungi

25. Green Fungal Hyphae in Wood

26. Blue Stain http://www.forestry.ubc.ca/brchline/98sept/page4.html

27. Mold on sapwood

28. Mold Species • 250 to 300,000 species • 45 species on Douglas-fir sapwood lumber in the first 6 weeks

29. Decay Fungus Fruiting Body

30. Brown Rot

31. White Rot

32. Damage by True Dry rot Fungus

34. Example of Decay Fungus in Culture

35. Soft Rot on a Utility Pole

36. Southern pine

37. Southern pine with soft rot

38. Soft Rot on a Eucalyptus pole

39. Decay Effects • Reduced bending strength • Reduced acoustic/insulation value • Increased permeability • Increased water absorption

41. Wood Destroying Insects • Carpenter ants • Termites • Beetles • Bark/Ambrosia • Metallic wood borers • Long-horned borers • Powderpost beetles

42. Carpenter Ants • Social insects (Queen/workers) • Use wood for shelter • Forage for food outside nest • Attack softer woods • Colonies <100,000 workers

43. Carpenter ant Worker

44. Carpenter ant Frass

45. Carpenter Ant Damage

46. Termites • Social Insects • Types • Subterranean • Wet wood • Dry wood • Light colored, small to large insect • Straight antenna • Unrestricted waist • Reproductives have wings of equal length

47. Dampwood termites • Require very wet wood • Colonies small (several thousand workers) • Confined to Pacific NW and Florida)

48. Dampwood Termites

49. Subterranean Termites • Require soil contact • Large colonies (1 to 5 million) • Produce mud-tubes

50. Subterranean termite Workers