DEATH WATCH BEETLE
This wood borer is no friend to old buildings, typically attacking oak and elm following decay by a wet rot fungus often Donkioporia expansa. Its control has to be carefully assessed and considered since dense hardwoods only absorb low levels of preservative fluid and continued attack can cause severe structural problems. Death Watch Beetle (Xestobium rufovillosum) causes structural damage as its boreholes at 3mm are a significantly greater diameter than the Common Furniture Beetle. Its life cycle, as destructive larvae burrowing within the timber, can be up to 12 years. Adults tap the timbers to try to attract a mate – occasionally clients contact us when they hear tapping but can see no evidence of infestation.
We look for fresh, brightly coloured, gritty bore dust and clean, dust free flight holes when establishing whether the infestation is active. As with all wood-boring infestation, a raised moisture content in the timber is key. Timbers likely to be affected by Death Watch Beetle are those most difficult to access, such as beam ends which are embedded into the structure.
Treatment in this situation must be seen as long-term and will usually involve monitoring to establish the level of activity. The following photographs show tissue paper stuck to timbers which when punctured identifies freshly emerging beetles in spring.
It remains essential to control the source of moisture and to promote drying of the timber and surrounding masonry. Death Watch larvae can survive at moisture contents of as low as 14%.
We would suggest targeted injection of the shakes, emergence holes and cavities together with surface application of specifically formulated paste preservatives. Resin-based techniques may enable timber to be repaired in-situ, retaining the original appearance and integrity. Existing floors can be stress graded and then structurally upgraded with resin, giving additional loading capacity. Replacement timbers, pre-treated will be fixed in cases where heavily infested timbers have to be discarded.
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