Asian lady beetle behaviour
Asian lady beetles were brought into the United States in large numbers in the 1980s to protect orchards from destructive insects, aphids in particular. They then headed north, reaching Canada. Asian lady beetles are now found on both shores of the St. Lawrence River, as far north as the Abitibi and Lac-Saint-Jean regions.
The Asian lady beetle (Harmonia axyridis Pallas) is recognizable by the two white markings near its head and, just behind its head, an M-shaped marking. The rest of its look varies: this insect may be yellow, orange, red or black. It may have up to 20 spots or none at all! The Asian lady beetle is larger (5mm to 8mm), more voracious and faster to reproduce than the varieties indigenous to Quebec.
Do Asian lady beetles live in groups?
Asian lady beetles behave in an unusual way: when autumn arrives, they cluster by the thousands on the outside walls of houses, looking for a way inside. In the spring, they do the reverse.
Are Asian lady beetles useful or bothersome?
Useful
- Asian lady beetles, like all varieties of ladybugs, are useful for your garden. They feed on many insects, such as aphids, that attack plants.
- They are themselves a source of food for some insects and animals.
- They do not sting, do not transmit disease and do not infest food supplies.
Bothersome
- They invade homes in large numbers (often getting in through cracks) to find warm places to spend the winter.
- When threatened, they can secrete an orangey fluid that has an unpleasant odour and can stain fabrics and surfaces.
- In the spring, they attempt to go outdoors to reproduce and can be seen congregating against windows and patio doors.
- The spread of the Asian lady beetle may be causing populations of native ladybugs to decline.1
- These insects are blamed for deterioration in the quality of wine when accidentally mixed with grapes during harvest.
1. For this reason, the Asian lady beetle is on the list of exotic species of concern (or potentially of concern) present in Quebec, drawn up by the Quebec Ministry of Forests, Wildlife and Parks.
Tips for keeping ladybugs away from your home
- Seal any holes or cracks in sun-facing exterior walls.
- Make sure window and door screens are in good condition.
- Install appropriate caps or mesh screens on exterior duct and vent openings.
- Make sure door frames are properly sealed.
How to get rid of Asian lady beetles?
A vacuum cleaner is the most effective tool for eliminating lady beetles from the house. Seal the vacuum bag immediately afterward and put it in the garbage.
Outdoors, pesticides are not recommended against Asian lady beetles. Their decaying bodies, possibly in very large numbers, will attract other insects.
To learn more about the Asian lady beetle
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PEST CONTROL TIPS (in French only)
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