Problems caused by Harlequin ladybirds

Why has the Harlequin ladybird become invasive?

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The Harlequin ladybird, Harmonia axyridis, has been used as a biological aphid control agent around the world. After being released in mass numbers due to their voracity towards aphids, this species rapidly spread throughout North America, Europe and South Africa.

In light of the exponential growth of the H. axyridis species, within record time, it became the most abundant species of ladybird present in many different habitats. In Belgium’s Wallonia region, within the past 10 years, it has become one of the five most abundant species found in agricultural habitats.

In addition to the fact that H. axyridis wipes out indigenous ladybird species and other aphidophagous insects, which causes ecological problems, the invasion of this ladybird has also brought about several nuisances in terms of economy and human health.

Problems caused in viticulture

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H. axyridis is considered a wine production pest. When their prey becomes rare in winter, the ladybirds gather and feed off the sugar produced by fruit. These invasions are particularly problematic for wine producers.

The economic losses may become substantial: ladybirds are very difficult to remove during the grape harvest. The insects that remain hidden in the vines are crushed with the grapes during the pressing and treading production stages. The toxic alkaloids contained in their bodies therefore contaminate the wine, which ruins the taste.

Problems caused in homes

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After the start of autumn, ladybirds start searching for a suitable place to spend winter and settle along our inner window frames and in curtain folds.

Once gathered in large numbers, this species can have a directly negative impact on humans. In addition to the unsightly appearance of a gathering of insects in one's home, the most bothersome nuisances are actually the hygienic issues and unpleasant smell they release. Ladybirds leave yellowish stains behind them on walls and curtains. Furthermore, they emit odorous chemical compounds that can provoke allergies, conjunctivitis and even hives.  

After being released in mass numbers due to their voracity towards aphids, this species rapidly spread throughout North America, Europe and South Africa.

What are Harlequin ladybirds?

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The Harlequin ladybirds belong to the Coleoptera order and are one of the Coccinellidae family.

They feed on aphids, psylla and cochineals with greater voracity than that of indigenous species, especially during larval stages 3 and 4 (eating up to 100 aphids per day!). These ladybirds have also been known to attack other local species of ladybird and other insects.

The Harlequin ladybird originates from China. After the start of the last century, particularly towards the late 1980’s, they were introduced to several countries (Europe, the United States, Canada) to harness their voracity (biological control agent against aphids, mites and other insects). Due to its high reproductive rate and resilience, it has become the most abundant species of ladybird observed in many habitats.

These ladybirds occur in a large range of colour combinations, ranging from red with black dots to black with red dots, as well as several shades of yellow. Their wings can have from 0 to 19 dots on them.

Prolific breeders, the females of this species can lay as many as 2,500 eggs in their lifetime at a rate of 20 to 30 eggs per day. In its first stage, a larva measures approximately 2mm and grows to around 10mm in its fourth stage. The larva’s colouring changes at each larval stage. Their chrysalis hangs from a high place, usually a leaf or a twig. An adult measuring between 5 to 8mm will normally live for 30 to 90 days, depending on the temperature.

They feed on aphids, psylla and cochineals with greater voracity than that of indigenous species.

Current solutions

Ladybirds pose a real problem for farmers and homes. Once they have settled on a fruit crop or in a house, the current methods used to eradicate them are either ineffective or even harmful (e.g. use of insecticides).

Current methods used in viticulture

The current method used for eradicating ladybirds from vines is mechanical. The idea is to shake the vines to make the insects flee (but they quickly return) and to rinse the grape vines several times in tubs of water before being crushed. This process is both costly (use of work force, waste of time) and increases the consumption of water associated with wine production.

Since the Harlequin ladybird has not yet developed a resistance to insecticides, some wine producers still use them to eliminate the ladybirds present in their vines. However, using insecticides does not resolve the problem because the dead ladybirds left behind often remain attached to the vines and therefore contaminate the wine. The dead bodies of the insects must therefore be removed using repeated rinsing processes. Furthermore, the use of pesticides can be even more costly in the long term because they may be toxic to humans and other nearby fauna, which can have a long-term impact on the vineyard’s ecology.

Current methods used in homes

The best eradication efforts have not been met with success: researchers advise vacuuming insect gatherings and placing them in the freezer to kill them. However, once released into the wild alive, ladybirds will immediately and instinctively return to their hibernating spot.

Once they have settled on a fruit crop or in a house, the current methods used to eradicate them are either ineffective or even harmful (e.g. use of insecticides).

Our solution 

Our aim is to propose an effective and ecological (pesticide-free) solution to limit Harlequin ladybird populations and therefore improve the quality of life of individuals and reduce losses for wine producers.

Little is known about the Harlequin ladybird’s chemical communication. Our methodology will be to study the means of chemical communication used by these creatures in order to lure them towards a trap and kill them without using toxic compounds.

By producing traps adapted for individuals and wine growers, DOMOBIOS will become a pioneering company in terms of developing ecological traps for controlling Harlequin ladybird populations.

Our methodology will be to study the means of chemical communication used by these creatures in order to lure them towards a trap and kill them without using toxic compounds.

Did you know?

Halloween Lady Beetle

In the United States, where the Harlequin ladybird first became an invasive species, it is called the Halloween Lady Beetle because Halloween is the time of year when it is most talked about as it prepares for winter. Most ladybird species take refuge in small groups in nature, whereas the Harlequin ladybirds prefer to hide within homes in their dozens, hundreds or even thousands.

Cannibalism

Both at adult or larval stages, these voracious (an adult can eat between 90 to 270 aphids per day) Polyphaga beetles mainly eat aphids. However, they sometimes feed on psylla, cochineals, fruit, or even the larvae of other ladybirds! Hence the fear that this cannibalism, which is fairly common among ladybirds, will affect indigenous species.

Our country has been invaded

In Europe, the Harlequin ladybird’s acclimatisation was first observed in 2001 in Belgium. Initially confined to the outskirts of large cities, sightings of the ladybirds quickly multiplied across the entire country, attesting to the species’ rapid expansion. In 2004, almost all of Belgium had been colonised.

Lifespan

The Harlequin ladybird normally lives between 30 to 90 days, depending on the temperature, but their lifespan can be greater than a year, and sometimes even three years!

Contaminated wine

Studies have shown that the flavours in wine can be altered if there is even one ladybird present per kilo of grapes. The ‘contamination’ threshold is therefore very low! This problem has led to substantial economic losses within the wine industry in the USA and Canada. In 2001, in Canada, a million litres of wine had to be discarded because of the bad taste caused by the presence of Harlequin ladybirds.

Contact

manhattan

Do you have any questions about this project? Are your vines infested with Harlequin ladybirds? Do you know of an infested vineyard? Is your house infested? Would you like to take part in this research project?

Please contact the CSO, Manhattan Solheid, at the following email address This email address is being protected from spambots. You need JavaScript enabled to view it..

 

Link to find out more about pests of all kinds

www.acari.be