The Asian ladybug has been attracting attention for several years. There are reports of desperate residents helplessly exposed to the plague in winter. So far, studies have given no indication that the Asian species is putting an end to native relatives.

The Asian ladybug has more points than the European one

Table of Contents

Show all
  1. the essentials in brief
  2. Pest or Beneficial?
  3. Pest control useful?
  4. Characteristics
  5. lifestyle and development
  6. dangers and challenges
  7. Preventing a spread
  8. frequently asked Questions
  9. the essentials in brief

    • The Asian ladybug was introduced as a pest controller, eating up to 5 times as many aphids per day as the seven-spot ladybug.
    • It is true that in some regions there are more Asian ladybirds than native seven-spot ladybirds; nevertheless, it is believed that there is currently no danger of extinction.
    • However, the Asian ladybird can harm the local ladybird when the food supply becomes scarce and it feasts on ladybird larvae.
    • Whether the Asian ladybug should be fought or not is controversial and has not been conclusively clarified; it does not pose a threat to fruit or vegetable cultivation.

    Asian Ladybug - Pest or Beneficial?

    The Asian ladybug is a prime example of the fine line between harmful and beneficial insects. Towards the end of the 20th century, the species was imported to Europe because, because of its great hunger for aphids, gardeners hoped for a targeted and efficient control of the pest.

    Actually, the supposed beneficial was only exposed in greenhouses. But the ladybug found its own way into the wild. Since then, the species has spread unhindered throughout Europe because it has no natural predators here.

    Conservationists fear that the Asian ladybird will crowd out the native seven-spot ladybird.

    No signs of extinction

    In some regions, the introduced species is more common than the native seven-spot ladybird, and plagues are not uncommon. Nevertheless, field studies could not give any indication that the invasive species is wiping out native ladybirds. The seven-spot ladybug is also very competitive and is an invasive species in North America. In studies in 2013, this species was more common in wine-growing regions than its Asian relative. But that varies from region to region.

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    Pest controller with a variable food spectrum

    The seven-spot ladybird can eat around 50 aphids a day, while its Asian relative can eat up to 270 aphids in a day. Thus, its role as a biological pest controller is extremely important. The Asian ladybug is not particularly picky about its prey. Even the toxins secreted by elder aphids don't bother the hardy species.

    In the absence of aphids, the Asian lady beetle changes its diet and preys on other soft-skinned insects, eggs and larvae. He feeds on gall midges, butterflies and becomes dangerous for native species of ladybirds. The beetle does not stop at conspecifics either. When food is scarce, both larvae and adult ladybugs will act aggressively and kill their counterparts with bites.

    Asian ladybug as an opponent:

    • destroys blood lice
    • decreases mealy apple aphid populations
    • eats hop aphids in large quantities
    • frees grapevines from phylloxera

    Asian ladybugs are used for pest control

    Unfoundedly feared in viticulture

    In autumn, the aphid colonies slowly retreat, so that the Asian lady beetle has to adapt to other food sources. It uses the high sugar content of grape juice as an energy source. The beetles magically attract fruit that has already been damaged. Therefore, grape varieties that tend to crack and ripen very late are particularly at risk.

    The beetles get into the wine production through the grape harvest. It is now known that the bitter-tasting hemolymph of the beetles has a negative effect on the aroma of wine. Pyrazines represent the main component responsible for this taste impairment. However, studies have shown that the taste effects are less than feared. With the Riesling grape variety, the recognizable taste threshold of the wine is four to five beetles per kilogram. With Pinot Noir, this threshold is between three and six beetles per kilogram.

    The same number of native species causes a significantly stronger change in taste in the wine. The substance of the hemolymph also occurs naturally in the grape varieties Merlot, Cabernet Sauvignon and Sauvignon Blanc. Only with the quality wine varieties Riesling, Pinot Noir and Müller-Thurgau is the so-called ladybug tone undesirable.

    Hardly any damage in fruit growing

    In the fall, ladybugs feed on fruit

    While the beetles appear as useful pest controllers on fruit trees in spring and summer, they transform into fruit eaters in autumn. During this time, the Asian ladybird feeds on various types of pome and stone fruit. Significant feeding damage has so far only occurred sporadically. There are reports from Austria of quality losses in fruit growing. Flavor changes can occur during the production of fruit juices.

    Soft-skinned fruit is at risk:

    • Ribes and Rubus: raspberries, blackberries, currants
    • Malus and Pyrus: late-ripening apple and pear varieties
    • prunus: plum, apricot, cherry, peach

    Highly effective bacteria inhibitors

    Scientists found that the Asian ladybug produces a natural antibiotic. This harmonin not only protects the beetle's immune system. It should also work against the pathogens of malaria and tuberculosis, which is why the suitability of Harmonin as a drug is now being researched.

    digression

    In this way, the Asian ladybug secures a survival advantage

    Asian ladybugs have an antimicrobial compound called harmonin. In addition, their immune system can defend itself against pathogens with over 50 different protein compounds. No other animal can produce as many antimicrobial peptides. The species is considered to be less susceptible to pathogens than the native beetles, which gives it a decisive selective advantage.

    In addition, the beetles make use of a kind of biological weapon, because their hemolymph contains microscopic spores of a parasitic protozoa. These fungus-like organisms belong to the higher classification Nosema. In the body of the Asian ladybug, the spores are dormant, so they do not further harm the species. Researchers suspect that the harmonine inhibits the proliferation of the spores and thus keeps them at a safe level.

    If a native ladybird eats the larvae or eggs of an infected beetle, the spores spread and multiply in its organism. Serious illnesses with a fatal end are the result. With this weapon, the introduced species displaces native representatives.

    Is pest control useful?

    The Asian ladybird multiplies rapidly and drives away native ladybird species

    So far, experts have not agreed whether the Asian ladybug needs to be destroyed. At least in Switzerland, the beetle has already displaced many native species. Here it is forbidden to deliberately release the Asian ladybug in nature.

    Be careful when sweeping away

    If you want to remove the beetles from the apartment, you can use a hand brush and dustpan to help. However, the beetles often feel disturbed. They defend themselves with the so-called reflex bleeding and secrete a yellowish defense secretion from the leg joints. The substance gives off an unpleasant odor and leaves yellow stains on carpets, floors, wallpaper and curtains.

    Therefore, use a broom that is as soft as possible so as not to bother the animals unnecessarily. You can then release the beetles outside, where they will die from freezing temperatures in winter.

    Soak up

    You can use the vacuum cleaner to remove the bugs in a convenient way. However, her life in the vacuum cleaner bag ends painfully with slow suffocation. Use a fresh vacuum cleaner bag to spare the animals this stress. You can then put the bag in the freezer so that the beetles freeze to death immediately.

    Avoid using chemicals

    An effective method of killing the beetles is the use of contact insecticides. Drugs containing pyrethrin or pyrethroid are lethal on contact. These are sprayed at the entrance gates of the hibernation quarters and only take effect when the beetles overcome the barrier. However, such insecticides are problematic because they are harmful to health and do not act selectively. Beneficial insects can also die from contact with the poison.

    Characteristics

    Asian ladybirds have significantly more points (usually 19) than European ladybirds (usually 7)

    Harmonia axyridis reaches a size between six and eight millimeters and is five to seven millimeters wide. The species is characterized by an extremely variable body colouration, ranging from light yellow to dark red. The elytra are black dotted.

    There are usually 19 points, some of which can be completely fused together, are weak or completely absent. In some beetles, the elytra appear to be black in color and dotted with red. This trait earned the species the nicknames Multicolored Ladybird or Harlequin Ladybird.

    pronotum:

    • colored bright yellow
    • black M or W shaped drawing
    • Pattern can cover the entire pronotum

    Distribution - in Europe and around the world

    The natural homeland of this species extends across East Asia. The beetle is found in China and inhabits southern habitats as far south as Yunnan and Guangxi. Other distribution areas are in Japan, Korea and Mongolia as well as in eastern Russia. In many areas, the species has been used as biological pest control since 1916, which is why the species can be found worldwide today. There seems to be a particularly high density of individuals near cities.

    identify larvae

    Very young larvae are initially yellow-green in color and have black bristles. Later, the base color darkens to blue-grey or black. Her body is covered with bristles. These so-called scoli have two to three branches. The orange-colored side areas, which develop in the course of the larval development, are striking. The coloring extends over the first five segments of the abdomen. The fourth and fifth abdominal segment also has an orange bristle on both sides.

    Differences between Asian and European ladybirds

    There are around 250 ladybird species in Europe, 82 of which are native to Germany. They colonize different habitats in which enough aphids live. This great diversity combined with the variability in body coloration and spot pattern makes identifying the species difficult. The most common native species can be easily identified by a few characteristics. In the Asian ladybird, the coloring of the pronotum is important.

    size base color drawing
    Two-spot ladybug 3.5 to 5.5 millimeters red or black two black or two to three red dots
    Seven-spot ladybug 5.2 to 8 millimeters Red seven black spots, two white spots on the pronotum
    Thirteen-spot ladybug 5 to 7 millimeters red, partly completely red or black thirteen black dots
    Dry Grass Ladybug 3 to 4 millimeters black yellow dots
    Sixteen Spot Ladybug 2.5 to 3.5 millimeters light yellow numerous black spots

    lifestyle and development

    The Asian ladybug can live up to three years. The beetles usually reach an age of between one and three months. Its development depends on environmental conditions and food availability. Although the beetles are often considered a nuisance, not all individuals survive.

    pairing

    Asian ladybugs mate in spring

    As soon as the first rays of sunshine in late winter warm up the earth and melt the snow, the beetles come out of their winter quarters and look for a suitable mating partner. Copulation can last anywhere from 30 minutes to 18 hours. The female usually mates with several males, sometimes visiting up to 20 partners. Mild temperatures influence the development of populations. Under optimal conditions, the species is able to form several generations per year.

    Offspring per year:

    • Great Britain: two generations
    • Greece: four generations
    • Asia: five generations

    egg laying

    A female can lay between 1,800 and 3,500 eggs in a lifetime. It seeks out plants infested with aphids. The females attach their yellowish eggs to the leaves in small packets of 20 to 30. Not all eggs hatch into larvae, many falling victim to unfavorable weather conditions or hungry insectivores. After three to five days, the larvae of the remaining eggs hatch.

    larval development

    The larvae need two weeks to fully develop into ladybirds. During this time, the offspring can eat up to 1,200 lice. They molt three times and then pupate directly on the leaf. The pupa usually rests open on the upper side of the leaf. After five to six more days, the imago hatches.

    wintering

    In their natural home, the beetles spend the cold season in crevices in the rocks. They fall into a hibernation and take no food. In Central Europe, the animals form large colonies on house walls in which they search for suitable winter quarters.

    A secreted scent causes the beetles to gather in large numbers. They keep an eye out for suitable cracks and crevices in which they are safe from frost. It is not uncommon for the insects to get lost in apartments and houses. However, they do not pose any danger to the buildings.

    dangers and challenges

    Despite the advantages that the Asian ladybug has over native species, it has to prove itself in nature. As conditions change, its survival advantage evens out. Scientists, on the other hand, are trying to help humanity by other means. Because the fact that the Asian ladybug can no longer be suppressed is considered a certain fact.

    enemies

    One of the rare natural enemies is the Forest Warden. The stink bug is predatory and hunts for insects and their larvae. They pierce the thin skin between the segments with their powerful proboscis, because they cannot pierce hardened chitin shells. They then suck their victims dry on the spot or carry them impaled to a safe place. However, the forest warden cannot manage to contain the population of the Asian ladybird alone.

    climate change

    The native seven-spot ladybird has been massively displaced by its Asian relatives in recent years. Contrary to dire fears from conservationists, the native species has been able to bounce back as temperatures soared. Studies have shown that the native beetles gain significantly more weight at higher temperatures than their Asian competitors.

    If the temperature rises by an average of three degrees Celsius, both ladybird species eat more than under normal temperature conditions. While the fat content and body mass of the seven-spot ladybird increase, the development of the Asian ladybird stagnates. The species follow different strategies in terms of energy use. The seven-spot ladybug saves its energy reserves for hibernation, while the Asian ladybug invests all its energy in producing offspring.

    As a result, in years with particularly hot summer months, there are extreme mass propagations of the Asian representative. However, many of them do not survive the freezing temperatures. These results show that at least the Asian beetle does not benefit from climate change.

    Wingless breeding

    French researchers have bred genetically modified variants of the Asian ladybug. These individuals do not develop wings and thus cannot spread uncontrollably. In France, these breeds are marketed as biological pest control.However, there is a risk that the specimens will cross with the wild ladybirds. The offspring can definitely develop wings again.

    Prevent spread

    Ladybugs get inside through the smallest cracks

    The most effective way to prevent the Asian ladybug from getting into your house and apartment is thorough prevention. Keep the bugs out by repairing cracks and damage to the facade. Even the smallest gaps are sufficient for the insects to get into the building. Roof overhangs and supply pipes can be fitted with insect screens, as can windows and doors.

    Are Ladybug Houses Effective?

    Insect hotels are commercially available that are specially designed for ladybugs. They should primarily offer the native species a safe shelter for the winter. Therefore, they are equipped with warming material and are placed in a sheltered location.

    Occasionally, the insect hotels are recommended as a shelter for the Asian ladybug. If there are large colonies on the house walls, a ladybug house will hardly help. The beetles will still look for suitable crevices in the facade or door and window cracks.

    fragrances

    So far, there is little reliable knowledge about effective substances for attracting or deterring. Affected homeowners consistently report that camphor and menthol have a deterrent effect on adult Asian ladybird beetles. However, the effectiveness of the secondary plant substances is short-lived, which is why the measure must be constantly renewed.

    tips

    To prevent insects from getting into the apartment, you can put sliced vanilla pods or bay leaves on the windowsill.

    Remove damaged fruit

    The Asian lady beetle changes its diet in autumn when the aphid colonies are slowly dying. They then feed on sugary fruit juices. In particular, damaged and eaten fruit of soft-skinned fruit is attractive to the beetles. Therefore, check your garden and remove such fruits in good time.

    Control in viticulture and fruit growing

    Contamination of wines and fruit juices by the ladybug can no longer be completely reversed afterwards. You should therefore check the trees and vines for possible infestation about two weeks before the planned harvest. Glued yellow boards are ideally suited to carry out inventory control. If necessary, the insects can be shaken off by hand before processing the fruit.

    tips

    Oak chips or activated charcoal weaken the ladybug tone in the wine.

    frequently asked Questions

    Are Asian Ladybugs Poisonous?

    Although the beetle emits a bitter substance that smells bad as a defense against enemies, the species does not pose any danger. It is not poisonous to dogs, cats or humans.

    It can happen that the animals are crushed by the grape harvest in wine production. As a result, the bitter substances also get into the wine, where they can cause changes in taste. However, this so-called ladybug tone is not harmful to health, but at best reduces the quality of the wine. Some grape varieties naturally contain the same substance that was also discovered in the defense secretions of beetles.

    Can the Asian ladybug bite?

    If the beetles get into a stressful situation, what is known as reflex bleeding occurs. They secrete a white to yellowish substance that is supposed to act as a deterrent. When panicking, the Asian ladybug is also able to bite. However, a bite is hardly painful and completely harmless to humans.

    How dangerous is the Asian ladybug for the ecosystem?

    So far, researchers have not agreed whether the invasive species can actually eradicate native ladybugs. There were always periods when the imported beetle appeared in large numbers and was superior to the seven-spot ladybug. Under changed environmental conditions, the populations of the Asian representative declined again in favor of the native beetles. In many places, however, the unwanted species is more common than the original beetle.

    Ladybugs can be found worldwide and can hold their own in different climate zones. However, they have one great benefit, as they keep various plant pests at bay. This makes it difficult to clearly classify the Asian ladybug as a pest or beneficial insect.

    How can the Asian ladybug hold its own?

    The species has decisive survival advantages over the native ladybirds. Researchers discovered an antibacterial substance in the haemolymph and around 50 different protein compounds. This enables the organism to defend itself effectively against pathogens. The Asian ladybird is less susceptible to disease than the native seven-spot ladybird.

    Another sensation is the existence of microspores of the Nosema type. The beetle organism keeps the spores at a safe level. If the beetle is eaten by a predator, the spores spread throughout its body. Infection leads to death in other insects.

    Where does the Asian ladybug come from?

    The original home of the beetle is in East Asia. There the species was used effectively as a biological pest control. For this reason, it was shipped to America in the 20th century, where it was used in greenhouses to control pests. This example was followed in Europe. However, it could not be ensured that the species did not reproduce independently outside the greenhouses (€72.95).

    In 2001, the first free-living specimen of an Asian ladybird was found in Belgium. Since then, the species has spread en masse throughout Europe. This development can no longer be reversed, as there are no natural enemies.