Woodworm in the roof truss - this is how you fight the pest

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Woodworm in the roof truss - this is how you fight the pest: roof

The woodworm is a particularly treacherous pest, as it lays its eggs in the wood interior. In turn, larvae hatch from the eggs, which develop into adult animals after a few years. During this time, they eat across the wood and damage it sustainably. If the infestation is not recognized and fought, this can even lead to the collapse of wooden structures. However, the pests can be recognized by typical damage patterns and fight by different methods.


The woodworm (Anobium punctatum) is also known as "common rodent beetle" and visually resembles the bread beetle. The pest is dark brown to reddish brown in color and reaches a size of about 3 to 5 millimeters in the adult stage. A special feature of this insect is the pronotum, which protects its head and acts as a hood. The woodworm is also able to fly and has heavily hairy elytra. However, before the beetle is fully grown, it spends several years in the larval stage. Characteristic of the larvae are the following features:
  • about 5-6 mm in size
  • Larvae are white and strongly curved
  • have strong jaws
  • they need this for wood eating
  • the mouth is colored brown

Development of the woodworm

If the wood provides the optimal conditions for the woodworm, it nestles in it as soon as possible and multiplies. Here, the females lay around 20 to 30 eggs in the cracks and crevices of the wood. Striking is the choice of location for oviposition: Because the pest is indeed capable of flying and can also cover more distances, but he prefers to lay his eggs in known areas. In particular, the females use the wood in which they themselves grew up. After the eggs have been laid, it takes about three weeks for the larvae to hatch and then drill into the wood.
  • Larvae eat the earlywood, but not the latewood
  • pupate between April and August
  • the adult beetle leaves the wood
  • look for a mating partner and multiply
  • Female lays the eggs again in the wood
  • this closes the cycle
The development from the larva to the adult beetle usually lasts around one to four years. In some cases, the larvae need up to eight years to fully develop, especially if the conditions are unfavorable. Because the development time depends on different factors such as temperature and humidity. In addition, the type of wood and its protein content plays an important role.

Preferred species and locations

The woodworm attacks both hardwood and softwood, the latter being preferred. Because especially the wood of pine, spruce and fir attracts the pest downright. In general it can be said that sapwood is especially popular with woodworms. This is more protein-rich than the heartwood and also rich in nutrient salts and water. The woodworm also nests exclusively in dead and blocked wood. However, the age of the wood does not matter, because the pest infects both centuries old and new wood structures. In addition, the following factors are crucial for an infestation:
  • high humidity and low temperatures favor infestation
  • prefers locations such as cellars, attics or barns
  • Minimum wood moisture of the wood over 10 percent
  • Heated living spaces, on the other hand, are hardly affected
  • because the wood is usually too dry
  • Wood moisture between 8-10 percent
  • except the wood is moistened too often
As a rule, the woodworm eats through the earlywood, which is formed in the spring. In contrast, the latewood spares the pest, creating a kind of lamellar structure. As a result, however, the wood loses its strength and, in the worst case, breaks up.

Schad pictures

Woodworm - Beetle

If infested with woodworms, it is worth trying to combat them yourself with different home remedies. A particularly cost-effective and environmentally friendly control method is the laying of acorns. These are laid out near the affected wood and attract the woodworms downright. It usually takes a few days for the pests to get into the acorns. This is recognizable at a hole in the glans and at meal. Once the pests have taken their new quarters, the glans is removed and a new designed. In addition to this method, the following procedures have been found to be effective:


The thermal treatment is ideal for smaller objects, where they are placed in the oven for about an hour. Afflicted pieces of furniture can be ideally heated in the car or in the sauna so that the pests die from the heat. Alternatively, summer offers the opportunity to use the sun for this purpose:
  • Cover object with black tarpaulin airtight
  • put in the outdoor area
  • Solar radiation heats the interior
  • This increases the temperature
  • and the pests are dying


The pests can be fought not only with heat, but also with frost. The advantage of this method is that, in contrast to the thermal treatment, it is much gentler on the wood. Because in this case, the moisture fluctuations are much lower, so that the wood is less stressed. However, the frost fight is only suitable for smaller objects, since the space in the freezer is usually very limited. To treat the infected pieces of wood with frost, proceed as follows:
  • Pack the object airtight in foil
  • then put in freezer
  • small / thin objects: 24-48 hours
  • larger / thick objects: up to 72 hours


Of course, different preparations are also suitable to combat the woodworms. However, these are to be treated with caution, as they can discolour the wood and attack the wood surface. Especially since not all preparations promise complete eradication of the pests. Boron salt is, for example, scattered on the affected wood and acts only superficially. Although it proves to be effective against young beetles, which leave the wood and thus come into contact with the salt. However, the larvae inside the wood can grow unhindered and continue to damage the wood. As an alternative to boron salt, it is also worth trying the sal ammoniac spirit:
  • kills larvae and adult animals
  • Place peel with the agent on the affected wood
  • pack airtight and seal with adhesive tape
  • Allow to act for a few days
  • can discolour wood!
Tip: Smaller wooden objects can also be treated with isopropnaol. Here, the wood is soaked with it and then packaged airtight with foil. After a period of two to three days, the pests should be killed.

Woodworms prevent

Woodworm damage

Since the woodworms prefer to settle in humid areas, the wood should always be stored dry. For outdoor storage it is advisable to protect the wood from rain with a tarpaulin. In addition, it should never have direct contact with the ground, as the soil moisture promotes infestation. If the wood is stored indoors, it should not be stored next to the fireplace. Regular airing also keeps the humidity in check, because this should be a maximum of 60 percent and possibly lowered with a dehumidifier. In addition, the following tips have proven to prevent:
  • weatherproofing agents for outdoor wood
  • prevent the wood from moistening
  • because they are water-repellent and light-protective
  • Check antique furniture for damage after purchase
  • ideally quarantine the first few days

Risk of confusion: Hausbock

The Hedgehog (Hylotrupes bajulus) also called ibex or Great Woodworm is another beetle whose larva likes to eat through the roof of a house. The beetle is one of the buck beetles and is therefore falsely referred to as "wooden buck", but what the name for the "tick". A domestic buck is between 8 and 26 mm long and has grown rather flat. Its color is from brown to black, finely hairy in gray and legs / antennae are brighter than the body. The larva from the house buck has these characteristics:
  • be up to 30 mm long
  • ivory-colored
  • clear structure
  • big head with 3 double-sided point eyes
  • powerful eating tool
  • Larvae live 4-18 years (depending on external factors)

Difference between woodworm and housebuck larva

The biggest difference between the two larvae of these beetles is that they are more likely to be affected by woodworm infestation. The larva from the housebuck clogs with their digestive residues their courses and does not let the wood flour out. This has the consequence that the infestation with Hausbocklarven is often noticed very late. You can hear the larvae but eat well, which can be attentive to them. If one detects an infestation, this must be reported in some federal states also (obligation to report is in the building code).

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