288 Chapter 11
after extensive examination of a large random timber sample, indicating that
fungal attack of stored polyethylene-wrapped timbers was very localised.
Bacterial decay was more frequently observed. Once again this form of decay
was also very localised. Erosion and tunnelling decay patterns were observed
in a number of timbers. The erosion troughs were observed below the outer
decayed surface layers, while the tunnelling bacteria were observed closer to
the outer cell layers. The possible explanation for the lack of active decay in
polyethylene-wrapped stored wood may be simply that unfavourable condi-
tions exist in timbers that are encapsulated in polyethylene. Oxygen levels
within the bags are very low, with little gaseous exchange across the polyethyl-
ene barrier. Also, with little or no exchange between the polyethylene barrier
system and the external environment, a build up of toxic substances and sec-
ondary metabolites takes place, thereby inhibiting the growth of fungi and
aerobic bacteria. The combined action of low oxygen and the presence of these
substances may explain the lack of recent decay by aerobic microorganisms
in polyethylene-wrapped timbers.
Breaches in the wrapping material may allow colonisation by wood-boring
insects. A survey of 1,568 Mary Rose timbers stored in polyethylene bags
revealed the presence of wharf-borer beetle larvae in 2% of these timbers.
Attack by this insect is not always apparent from examination of the timber
Table 1Marine fungal species isolated from
Mary Rose timbers
Species Decay type
Ascomycotina
Corollospora maritima Soft rot
Lulworthia sp. Soft rot
Neriospora cristata Soft rot
Zopfiella sp. Unknown
Deuteromycotina
Cirrenalia macrocephala Soft rot
Dictyosporium toruloides Unknown
Gliomastix mucorum Unknown
Humicola alopallonella Soft rot
M. pelagica Soft rot
Penicillium sp.* Staining
Stachybotrys atra* Staining
Trichocladium achrasporum* Soft rot
Zalerion maritima Soft rot
Zalerion varium Soft rot
Basidiomycotina
D. maritima White rot
N. vibrissa White rot
* Terrestrial species.