A local museum contacted me recently about Powder Post beetle infestation that they had been dealing with for a few years. They have several older wooden buildings with lots of small and large wooden objects housed within. They have been spraying every year with a product called Tim-Bor. The results have been encouraging with much less infestation over time but not yet completely solved. These beetles bore into wood and deposit eggs. When the eggs hatch the larvae eat their way out of the wood, mate in the spring and the cycle starts again. They had asked me about the best way to deal with new objects coming into the museum and any existing objects that may be infested.
How do you know you have a beetle infestation? Here are a few photographs of holes in wooden objects and a photograph of the dust which is a combination of sawdust and frass (insect excrement).
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| Beetle holes - mallets |
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| Beetle holes - pulley |
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| Beetle dust - stairwell |
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| Beetle dust - barrel base |
There are several kinds of beetles that exhibit the same characteristics that can be treated the same way. Spraying with a boron based product such as Tim-Bor, Borasol, or Ambush every year for several years will reduce the population and keep it under control. Watch for beetle activity evidence such as the dust as shown in the photographs every year usually in summer or late spring. Spray all the wooden areas (walls, stairwells, doors) and the larger objects. These products are easily handled but require basic handling equipment to apply. Refer to the safety data sheet for any of these products first before usage.
Any wooden objects of a small size can be treated by depositing them in a freezer for a minimum of two weeks. Such things as wooden mallets, pulleys, wooden handled tools, and the like which can fit in the freezer are good candidates. Wooden wagon wheels, carts, poles, and the like are usually too big so should be handled differently. Maintaining a low temperature over two weeks will kill off any of the eggs, larvae, or beetles present in the wood. There is some variance but typically, freezers maintain a temperature of around -18C. Since beetles are active in the spring and lie dormant over the winter they are able to handle fluctuation in temperatures but not a sustained cold temperature. Our winters in Nova Scotia have fluctuating temperatures between freezing and thawing so our beetles have adapted to that environment. After two weeks you can put the objects back into the collection where appropriate.
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| Beetle holes - wheel |
For larger objects such as the wagon wheel shown in this photograph I suggest spraying them every spring around middle of June for Nova Scotia which is their optimal time for reproduction. They tend to be active, moving toward sunlight at that time. Around this time you should see evidence of their activity - either bore holes or dust. Sometimes the bore holes may not be visible until the spring because the object has been sanded and painted.
All new wooden objects coming to museums should be carefully examined for evidence of pests. If so, they should be bagged and isolated for a period of time to determine if they are actively infested. Bagging will allow for any evidence of activity to be observed. If they can be stored in a non-wooden environment for a time this would be best. If they are small they can be put straight into a freezer for two weeks. Larger objects with bore holes should be sprayed and examined in late spring or early summer for evidence of beetle activity.
Conservation Tip
With respect to preventive care - objects in collections should be examined as a minimum at least twice per year. Wooden, textile, paper or leather objects for pests and mold; metal objects for tarnish and rust. Identifying problems as soon as possible can prevent more serious infestation or damage that would be more difficult to treat if left undiscovered. Careful examination will then determine what treatment is necessary, the costs in terms of materials and time, and then a plan to implement the treatment.
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