Long-horned beetles are among the most dangerous pests that tamper with wood. But an infestation is often only discovered when the damage is far advanced. Early detection is not hopeless, because the larvae reveal themselves through certain damage patterns.

The larvae of the wood longhorned beetle like to eat wood

Table of Contents

Show all
  1. the essentials in brief
  2. harmful pictures
  3. assessment of an infestation
  4. combat
  5. Characteristics
  6. lifestyle and development
  7. longhorn beetle species
  8. food
  9. Happen
  10. frequently asked Questions

    11. the essentials in brief

    • If you discover a house borer infestation, you should report this immediately to the building authority - there is an obligation to report
    • The longhorned beetle reveals itself by piles of wood flour at the foot of the infested pieces of furniture
    • Thermal control is the most environmentally friendly, e.g. with heat in the oven or sauna or with cold in the garden when the temperature is below zero
    • Combating with chemical agents is not recommended and is less efficient

    Identify infestation through malicious images

    Long-horned beetles are able to severely damage built-in coniferous wood in a very short time. In Germany, the house longhorn is considered the most dangerous wood destroyer in the house, which is why in some federal states a reporting obligation has been established in the building regulations. If you notice an infestation, you should immediately contact the responsible building authority.

    tips

    When building a house, choose wood with a minimum heartwood content of 90 percent. This is attacked neither by the house longhorn nor by the woodworm.

    signs of an infestation

    The feeding activity of the long-horned beetle is much more difficult to detect than feeding damage caused by the woodworm (Anobium punctatum). The house longhorn clogs log passages with sawdust and droppings so that no tell-tale piles of wood flour are left behind. These corridors will not be entered again.

    In the case of a severe infestation, a thin wooden skin remains that can be easily scraped off and reveals the tunnel system. The only external distinguishing feature of infested wood are the oval exit holes of the adult beetles. These are between four and seven millimeters in size. Feeding noises are a clear indication of an active infestation.

    digression

    Track down the house goat with search dogs

    Since 2008, tests have been carried out in Australia with detection dogs, which are intended to detect an infestation by the house longhorn at an early stage. To this end, two Labrador dogs were specifically trained. Their fine sense of smell should make it possible to identify the beetle larvae in the wood up to three years earlier. Conventional measures such as searching built-in wood only provide reliable information when adult beetles have already found holes to escape. Then they may have already reproduced and laid new eggs.

    assessment of an infestation

    A wood tick infestation is often only discovered very late

    Before measures are taken to combat the infestation, the infestation must be checked and ensured by a specialist. The house longhorn is not always a pest for feeding marks in the wood. Other insects also leave tunnels in roof beams.

    Wood age and endangerment

    During an infestation check, the intensity of the infestation and the age of the wood on the undamaged beams are checked. Statistically, it is very unlikely that lumber around 60 years old will be affected. This means that wood protection applied later is of no use.

    The attraction of the wood species is very strong in the first 30 years and then steadily decreases. After 100 years, wood is hardly endangered and 140-year-old timber is only attacked in rare exceptions. Nevertheless, an infestation cannot be completely ruled out, even with old wood. If the males only find impregnated wood, they also set their scent marks on atypical old wood. In addition, fresh repair wood can increase the attractiveness again.

    The older the wood is, the less likely it is to become infested. However, this cannot be completely ruled out.

    Beware of dubious experts

    It is not uncommon for companies to take advantage of the ignorance of the public and carry out nonsensical or overpriced countermeasures. There are often so-called door-to-door sales, in which residents allow themselves to be taken by surprise by self-appointed experts and sign contracts out of concern.

    In some cases, the infestation is so severe that the advertised control methods are no longer effective and the entire roof structure has to be replaced. Many measures are also pointless if the infestation has already died out or is only very weakly developed. Expensive control measures are offered less frequently, even if wood damage has been caused by other harmless insects such as the wood wasp or the longhorn beetle.

    combat

    In the event of a positive control, different measures are taken depending on the intensity. The pests are often controlled with chemical agents. Contact insecticides are not always the best solution as they make it difficult for pests to reach them. Effective control is carried out using the hot-air method at high temperatures. Smaller items can be heated in the sauna. In a microwave with a built-in horn heater, the wood can be irradiated and overheated for several minutes, so that all living things containing water are killed.

    Chemical control:

    • File down and impregnation of the wooden surfaces
    • pressurized or pressureless injection
    • Fumigation with sulfuryl fluoride

    tips

    To kill all life in the wood, you should heat the piece of furniture to 65 degrees Celsius for one to three hours. Proteins in the body begin to coagulate at around 60 degrees Celsius, causing the organism to die.

    Characteristics

    The wood longhorned beetle is not very conspicuous

    The longhorned beetle, which is incorrectly called the longhorned beetle for short, belongs to the longhorned beetle family. The beetle can be recognized as such by its long antennae, which are slightly bent backwards. Because of this typical feature, the family got the German trivial name. Behind the long-horned beetle is the species Hylotrupes bajulus. Loosely translated, this species name means something like “the one that drills in the wood of the wearer”. This expression indicates the way of life of the beetle.

    A beetle with many names:

    • beam stand
    • house goat
    • Big woodworm

    Typical characteristics

    Adult beetles are between eight and 26 millimeters long. The body is comparatively flat. Color and markings may vary between individuals. The basic color is brown to black, with legs and antennae usually appearing a little lighter. The entire body is covered with fine and greyish shimmering hair. In some animals the elytra clearly show two pairs of white hair spots. These can be more or less intensively developed.

    anatomy

    Longhorned beetles have a strongly rounded pronotum with two shiny calluses on the upper side. The pronotum is significantly wider than the head. The thickened thighs of the legs, whose claws have small teeth, are striking. For a longhorn beetle, the house longhorn has comparatively short antennae, with the third antennal segment being longer than the fourth.

    larva

    Longhorn beetle larvae can reach a length of up to 30 millimeters. Their ivory-colored body is clearly articulated and ends in a larger head that has powerful mouthparts. Next to the eating tools there are three point eyes. If they are not disturbed, their noises, made by scraping the wood fibers, are clearly audible. They can be used as a sure sign of wood infestation. At the slightest disturbance, they stop eating and fall silent.

    lifestyle and development

    Between May and August, the beetles are looking for a mate, and they only live for about four weeks. During this time, the house longhorn takes no food. Since it is a dry wood insect, the beetles only lay their eggs in dried and mostly built-up wood.

    wood search

    Immediately after hatching, the females go in search of a suitable place to lay their eggs. She uses the escaping aerosols to assess the suitability of different types of wood. Males also look for a suitable and protected area in the wood that is suitable for mating. They then produce a sex attractant to attract a female willing to mate. However, these are also influenced by the intensity of the fragrance of the wood. In this way, the females try to find the wood that offers optimal development opportunities for their offspring.

    pairing

    The female lays eggs two to three days after mating. These are placed in small cracks in the wood using a flexible tube. Even the smallest gaps with a width of 0.3 millimeters are sufficient.

    Within the framework of an egg-laying process, six to eight clutches are formed, each containing an average of 50 to 60 eggs. In total, females can lay between 140 and 200 eggs. Individual females produce more than 500 eggs. Males die shortly after mating, while females die after laying their eggs.

    A single female lays between 50 and 60 eggs

    development cycles

    The larvae eat their way deeper into the wood shortly after hatching. They go through several growth cycles between which they molt, whereby the duration of the larval development is influenced by various factors.

    After the last larval stage, pupation occurs just below the surface of the wood. The larva undergoes metamorphosis and hatches as a sexually mature beetle. It usually takes four to six years for the larva to develop into an adult beetle. If the larvae live in nutrient-poor wood, the development can extend to twelve and in rare cases to 18 years.

    This influences the larval development:

    • nutrient: high protein content important
    • humidity: ideally between twelve and 30 percent
    • temperature: Optimum between 28 and 30 degrees Celsius
    • wood type: prefers softwoods such as fir, pine or spruce

    Species of the longhorn beetle

    The European long-horned beetle is easy to recognize and hard to confuse with other species. The biggest misunderstandings arise from misleading naming of different species. The wrong designation common wood long-horned beetle occurs occasionally. This name probably came about as a mixture of the tick species common wood tick and the long-horned beetle from the long-horned beetle family. There are a number of other longhorn beetles that appear as pests.

    scientific name further designations damage Recognize
    Asian timber-horned beetle Anoplophora glabripennis Asian long-horned beetle Deciduous and fruit trees black with light spots
    Chinese wood-horned beetle Anoplophora chinensis citrus longhorned beetle Deciduous trees, preferably citrus plants black with light spots
    Common longhorn beetle Stictoleptura rubra Red Collared Goat Softwood, preferably spruce and pine bright reddish brown

    The red-necked buck doesn't just have a red neck

    food

    Longhorned beetles only infest softwoods such as pine and spruce, fir and larch or Douglas fir. Hardwoods secrete substances that kill the larvae. These feed mainly on the sapwood, which is in the outer areas. Occasionally they undertake exploration tours to the inner heartwood. But this is largely avoided. The reason for this behavior is the nutrient content of the wood. The nutrient content in the outer annual rings is significantly higher than in the heartwood. The lower the protein content, the slower the larvae develop.

    Happen

    The range of the long-horned beetle extends across the entire Palaearctic. The wood pest was carried to North America, South Africa and Australia by humans. Females only lay their eggs in dead coniferous wood, so their larvae can benefit from the nutrient-rich sapwood. The beetles are often found in the built-in wood of roof structures or wooden facades, as the conditions here are optimal for development. There are often already eggs in the firewood or in the fireplace wood, so that the pests can easily be introduced.

    frequently asked Questions

    What does the house goat look like?

    The wood pest, which belongs to the longhorn beetle, has a variable body that can grow to more than two centimeters in length. Its relatively short and backward-curved antennae are typical. The beetle is brown to black in color and hairy. Sometimes white patches of hair are visible on the wings. The thickened thighs are another distinguishing feature.

    Can you confuse the wood longhorned beetle?

    It is almost impossible to mix up the adult beetles, since all other long-horned beetles look different. The ash gray evening buck (Trichoferus holosericeus, synonym: Hesperophanes cinereus) is sometimes referred to as a wood buck double. This species was introduced from warm regions and only inhabits deciduous trees. Adult beetles can be identified by their coloration. This doppelganger has a reddish-brown basic colouration, which is however hidden by the intense gray to whitish hairs. As a dry wood insect, this species also causes damage to the wood.

    How do I recognize an infestation by the wood longhorned beetle?

    An infestation often goes unnoticed until the first exit holes become visible on the wood. Then the larva may have already caused major damage. A first sign of an infestation are feeding noises coming from the beams. They are reminiscent of scratching and scraping, which occurs when the edges of the thumb and middle fingernail rub together. Some bulges are visible on the wood surface.

    You should pay attention to this:

    • paper-thin layer of wood can be easily scraped off
    • corridors filled with dusty sawdust appear
    • typical corrugation on the aisle walls

    Why do the sounds of the house longhorn larvae stop when disturbed?

    The larvae are extremely sensitive to noise, as one of their natural enemies is the woodpecker. It looks for its food by tapping on the wood and looking for insects and larvae. Longhorn larvae fall silent at the slightest disturbance so that no predators will notice them.

    How can I prevent a house borer infestation?

    Choose native wood species that are resistant to infestation by the long-horned beetle. Heartwood from larch, pine and Douglas fir, which has a maximum proportion of ten percent sapwood, ensures optimal prevention. Equally, crack-free, dry timber protects against infestation. If you cannot do without spruce or softwood timber rich in sapwood for cost reasons, you should treat it with a chemical wood preservative before installation.

    How to protect wood:

    • do without heat-storing wooden formwork
    • Wooden structures must be well ventilated
    • Do not wall in wood to avoid moisture accumulation
    • don't dry laundry in the attic
    • Close attic hatches during flight time

Category:

Animals in the garden