General Features of White Rot and Brown Rot Fungi

2

Introduction

Plant matter is constantly under attack by fungi, insects, bacteria, marine borers and the weather.

It is estimated that roughly 1/10 of the forest products generated each year are destroyed.

Wood decay or wood rot is caused by fungi – organisms that live on other organic matter such as wood.

While this can be bad, without these processes we would be buried in a sea of old dead plant matter.

3

OccurrenceDecay of timber occurs only when wood is allowed to remain

permanently or regularly damp. Decay is described as either wet rot or dry rot; although both

can occur together in damp wood.Can develop on susceptible wood if the moisture content of the

wood remains above about 22% regularly for prolonged periods.

Develop from minute airborne spores which germinate if they land on a suitable substrate such as damp wood.

Produce thread-like hyphae, which collectively form a mycelium.

The hyphae making up the mycelium penetrate the wood, breaking down the wood cell walls and feeding on them.

Mycelium produces a fruit-body; this releases spores to the atmosphere, completing the life cycle.

4

Types and FormsWhite rot - all components removed Brown rot - primarily carbohydrates lost, lignin mostly remainsSoft rot - carbohydrates preferred, but some lignin lost tooSlash rot - decay of dead material left behind after logging

PositionsHeart rot - decay in the stem that develops primarily in the

heartwood or inner wood of living trees Sap rot - saprobic decays that develop in the sapwood Butt and root rot - decay primarily in the roots or at the base of a

tree heart rot - decay in the stem that develops primarily in the heartwood or inner wood of living trees

5

Types and Forms (Cont’d)

6

White Rot Fungi

This group of organisms is known as white rot because of their ability to degrade lignin. Can delete up to 100% of Timber weight.

The decaying wood looks white.

Cellulose and hemicelluloses are also degraded.

Generally decay occur from lumen outwards.

White rot fungi typically decay hardwoods They will decay softwoods but hardwoods are their food of choice.

7

White Rot Fungi (Cont’d) Largest number of species belong to Basidiomycotina Xyariaceous and Diatrypacsous also numerous.

8

Brown Rot Fungi With brown rot fungi, cellulose and hemicelluloses are degraded with

only limited lignin degradation. Can delete up to 65% of timber weight. Decayed wood is brown and crumbly.

Brown rot fungi typically decay softwoods.

Attack starts at the cell lumen and works outwards. Cellulose is rapidly degraded.

9

Brown Rot Fungi (Cont’d) Most species belong to Basidiomycotina.

10

Features of white and brown rot

11

Defense Against Decay

Wall thickeningPhenolic chemistryWound peridermProgrammed cell deathOuter physical/chemical barrier Bark/cuticle

H2O, O2, N limits

Heartwood chemistry Extractives

12

Benefits

Woody says, Fungi are great! I wouldn’t have a home without them!

THANK YOUFor Your Attention!