Latin: Hadrobregmus pertinax, Coelostethus pertinax and Dendrobium pertinax
Hadrobregmus pertinax also referred to by the names Coelostethus pertinax and Dendrobium pertinax so it is a beetle with several names. The beetle belongs to the wood boring beetle family – more precisely Anobiidae.
Appearance
The beetle is 5-6 mm long and the color is black with strips on the cover wings. In addition, the beetles have a couple of spots of yellow silky hairs on the back corners of the chest. If you are in doubt of the species of a specific beetle, these yellow spots will be characteristic for the Hadrobregmus pertinax. Its head is hidden under the neck shield. The larva is c-shaped and is white with yellow hairs.
Biology and behavior
To attract the females, the male makes a ticking sound, by banging his head against the woodwork. After mating, the female lays about 10 eggs, which are placed in cracks in the tree. The preferred cracks consist mainly of old fly holes or passages, where the newly hatched larvae will immediately drill into the wood. Throughout the rest of their larvae stage, they will stay inside the wood slowly eating through the it. The larval passages are less than 3 mm wide and follow the annual rings of the tree. The development of the individual larva depends on variables like temperature, humidity and the quality and nature of the wood. The larva will usually be fully grown after two or three years.
Once the larva is fully developed, it will pupate, which happens in the fall, and within a few weeks, the pupa will have developed into an adult beetle. However, the beetle will remain inside the tree until May-June, and then it will emerge from the tree, through a characteristic fly hole of a diameter of 2-3 mm. The dust from the fly hole will be dark yellow, as the wood the beetle feed on is rotten.
The natural habitat for the beetle is rotten coniferous trunks or branches. But they can also be found in fence posts. The adult woodboring beetle overwinter inside the wood.
Damage
The woodboring beetles attack wood that has been softened by fungus or rot. Places to find the beetle are most other completely sealed tree like beams and rafters. The larvae do not thrive in wet wood. Therefore, the beetles only attack once the rot has stopped.
If wood is attacked by Hadrobregmus pertinax, it can in many cases get turned into powder. Afterwards it will only be the hardwood that is left, standing as a thin shell. The beetles can therefore do great damage, and most homeowners does not consider them as a welcome guest.
Prevention and control
The cause to most cases, regarding infestations of the woodboring beetles are always caused by water or other forms of moisture. They key for prevention is supervision of pipes and roofs including ensuring an effective ventilation.
If a infestation by the woodboring beetles is detected, the key is finding the source of the moisture and repairing it. It is not known for certain if the beetle can continue its attack when the wood has been dried out. You should consider this if the attacked wood is particularly valuable. If valuable wood has been attacked, one should either treat or replace the wood.
Treating infested wood is done with wood preservatives. The chosen preservative should work against both insect infestation and fungus. It is recommended that the preservative is either painted or sprayed directly on the infested wood. It may be necessary to drill smaller holes in the wood in the case of dense timber. For the best result, fill the holes with the liquid. If it is necessary to replace the damaged woodwork, the new inserted wood must be treated first. An advantage is pretreated wood, but you can also soak the wood, paint or spray an approved agent against wood pest on the replacement wood. It is a good idea to use wood with the least possible amount of sapwood in exposed areas, as sapwood is more unprotected to insect and fungi compared to hardwood.
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