What are Asian Lady Beetles?

The multicolored Asian lady beetle is a common pest throughout Ontario, and other parts of Canada. Its scientific name is Harmonia axyridis (Pallas), and it is from the large family of ‘Coccinellidae’ beetles.

Many people call these beetles “ladybugs”. But not all ladybugs are created equal, especially when there are around 5,000 ladybug beetle species worldwide. The Asian ladybug is aggressive and a nuisance in late fall, winter, and spring. Country areas, and wooded residential & industrial areas are especially prone to having severe infestation problems. These pests can spread over time and may be more difficult to rid as time passes.

The Asian lady beetle is a pest native to Asia, where it lives in trees, fields and orchards, and feeds on aphids and scale insects. It is believed that this beetle species was first mass introduced to the north eastern United States in the 1960s by the U.S. Department of Agriculture in an attempt to establish the Asian ladybug as a natural control mechanism for agricultural pests. They would reduce the need for pesticides for hardwood forests, roses and specific crops, like cotton apples, pecans, peaches, alfalfa, and corn. There are some scientists who believe they were introduced earlier to the U.S. by accident via a freighter from Japan to New Orleans.

Asian lady beetles have now become a nuisance pest in other crops in the U.S. and Canada, and to people. They do not appear to have many natural enemies. A few have been known to be parasitized by tiny flies and wasps. While they have a higher mortality rate in regions with sub-freezing temperatures, they have been able to adjust and survive by seeking out protective shelter in buildings.


What Do Asian Ladybugs Look Like?

Adult Asian lady beetles are small (about 7mm) and oval shaped.

Their colours vary in shades of red, yellow, orange, and tan. The most common colour is deep orange. While many Asian lady beetles have black spots on their back, some have none.  They are distinguished from other ladybug species by their large white cheeks and a black "W" (or "M", depending on your viewpoint) on its head. Other ladybug species have a black head and may have white marks on their cheeks, but they will be much less pronounced.

The Multicoloured Asian Lady Beetle on a leaf

Asian Lady beetle eggs are oval and yellow in colour. The larvae are commonly orange and black, and look like small alligators.


Are Asian Lady Beetles the Same as Ladybugs?

Asian lady beetles are often mistaken for the docile, good-luck bringing bright red ladybug While ladybugs are generally considered beneficial because they live and feed on plant pests outdoors, the Asian Ladybug is an aggressive beetle, and a nuisance to other crops and to people. They have been known to swarm and bite in masses. They also secrete a foul smelling yellow-coloured fluid from their leg joints when they feel threatened, and to help warn off predators.


The Asian Lady Beetle Life Cycle

The Asian lady beetle goes through four stages in its life cycle - egg, larva, pupal and adult. The average time from egg to adult is 1-2 months. Depending on the region and habitat, they can produce more than a single generation per year, and live up to three years.

Female Asian lady beetles lay their eggs in spring and early summer. Eggs are laid in clusters on the undersides of plant leaves near colonies of aphids, mites and scale insects, which will be the main food source for the larva once hatched. A single female can lay up to 1,000 eggs. On average, the larva hatch after 5 days, and seek out nearby food. As a larva grows, it sheds its outer skin (or molts) around four times before making its transition from a larva to a pupa. The pupa is a shiny golden colour, and appears wets. It is extremely vulnerable at this stage while it awaits for the hardening of its exoskeleton. Once hardened, the Asian ladybug is now an adult, and will reveal its true colours and markings. It will continue to live outdoors and feed on aphids, mites and scale insects until the fall when it seeks overwintering sites.


Do Asian Ladybugs Bite?

Yes, Asian lady beetles have been known to bite, or more specifically, ‘pinch’ exposed skin with their chewing mouthparts. This can happen upon landing on a human or pet, if they are handled and in self defence in they feel threatened. The bite has been described as a pinprick and is rarely serious. 

They do not carry or transmit diseases, however there have been instances and studies suggesting Asian lady beetles can trigger allergic reactions. Reactions are caused when a person is around a large infestation, or by touching them and subsequently touching one’s eyes. Documented allergic reactions range from conjunctivitis (pink eye), cough, hay fever, hives and triggering asthma. It is important to wash your hands if in contact with Asian lady beetles and to avoid touching your eyes (and face) if you have made contact.


Do Asian Lady Beetles Cause Damage?

Asian lady beetles are a nuisance pest. They do not feed or reproduce indoors, nor do they attack buildings, furniture or fabrics. They do release a pungent bitter smelling odour and leave a slimy yellow-coloured stain on any surface or material they are squished on.

Asian ladybugs have become a more serious concern for the wine industry in Eastern and Midwestern U.S. and Ontario, Canada. In the fall they take shelter in wine grape clusters in vineyards. If any beetles are accidently processed with the grapes their harsh, their acrid odour can taint the wine’s flavour.


Why do Asian Ladybugs Infest Homes?

Like many other overwintering pests such as the boxelder bug, pine seed bug and cluster fly, the Asian lady beetle seeks protective shelter in the late summer and early onset of fall, (from mid-September through October) to overwinter. They love to bask in the late summer sunshine and will gather in considerable numbers on the south sides of nearby buildings and structures. As the fall weather cools they seek warmth and protection in nearby cracks, crevices and gaps, finding their way into homes and commercial building. Once inside, they congregate in attics and wall voids, which are quiet and safe, and remain dormant until spring.

Asian ladybugs are believed to be most attracted to buildings and structures that:

  • are near woods and fields
  • are illuminated
  • are light colored
  • have a contrasting light and dark colour scheme. For example, light grey siding and black shutters.

If they find a favourite overwintering site, they can produce an attractant pheromone which can stimulate the beetles to return to the same location year after year.



What are the Signs of a Asian Lady Beetle Infestation?

The most obvious sign of an Asian ladybug infestation indoors is the appearance of large numbers of beetles around windows, doors, and light fixtures, as well as on walls and ceilings in the spring, or even on warm winter days. A concerning sign, which may be a signal that an infestation could happen, is when huge masses of Asian lady beetles are found congregated outside of human inhabited buildings and inside cracks and crevices of the siding and trim.


How To Get Rid of Asian Lady Beetles Effectively

Similar to other overwintering nuisance pests, prevention in both fall and spring is the best approach for getting rid of Asian ladybugs. Pest proofing your home or business helps reduce the chances and quantity of beetles that gain entry to your premise. Here is a list of preventative maintenance items that you can do to help keep Asian lady beetles outdoors:

  • Seal small exterior cracks, crevices, gaps and holes with a good quality silicone or silicone-latex caulk. Plug larger holes with copper mesh, cement or urethane foams. Focus on these places:
    • Windows, doors, siding, eaves, fascia boards and overhanging vents.
    • Roof joints and behind chimneys.
    • Places where utility pipes, plumbing, wires or cables enter the building.
  • Fix, replace or install window and door screens.
  • Fix, replace or install screening behind attic vents.
  • Fix, replace or install screens in roof and soffit vents.
  • Replace damaged weather stripping around doors, install if absent.
  • Install door sweeps on exterior doors.
  • Inside the home or building, patch any holes that lead into the attic.

If you are serious about how to get rid of Asian ladybugs effectively, seek professional pest control help to treat the perimeter of your home and building with a residual spray in the spring and fall. A licensed pest management technician will also help uncover the root problem and use integrated pest management techniques to help rid you of the pests, monitor for them, and most importantly, prevent them from returning.

Be cautious about advertised ladybug light traps, ladybug houses and repellents. First, traps and houses do not prevent the pests from entering or infesting your premise. Light traps have limited effectiveness and are known to deliver best results in attics, when beetles are active. Lady bug repellents have been said to be effective in small areas. They often include alcohol, garlic oil, mineral oil, menthol, capsaicin or camphor, and require frequent reapplication and have been known to help in small areas. You will need to have a firm grasp over the entry points in your home or building to be able to accurately apply the repellent.

Unfortunately, once you have an Asian lady beetle infestation, there is no fast and easy solution.  You will likely experience an annual pestering from them, which will dramatically lessen with routine treatments and ongoing prevention from an experienced pest management professional.


How to Control an Asian Lady Beetle Infestation?

If Asian lady beetles are invading your spaces you can gain temporary relief by using a vacuum, broom or sticky tape to address visible beetles. After vacuuming, be sure to dispose the bag or empty the canister outdoors. Similarly, after sweeping up the beetles, dispose outside. If you threaten Asian ladybugs they will release their harsh smelling odour, and if you squish or swat them, they will leave a yellowish stain.

The best method of control is through prevention. We unknow first-hand that comprehensive pest proofing is not always possible. It can be too time-consuming or even impractical. When faced with an unbearable infestation, seeking help from an Asian lady beetle pest control professional is your best approach for getting rid of Asian ladybugs.

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