Master_gardener_07-43

Jeff Green | Nov 01, 2007

Back toHome

Master Gardener: Asian Lady Beetle Invasionby Ankaret Dean, Lanark County Master Gardener

The little red ladybeetle, a.k.a. ladybug or lady bird, has long been a favourite insect, known as a friend who helps protect gardens and orchards by consuming thousands of aphids. The native species do not sting, transmit diseases or infect food supplies, and of more that the 450 species of the ladybugs in North America, only three feed on plants.

However, the multicoloured Asian lady beetle (Harmonia axyridis) has become a major problem for many households in spring and fall. This beetle was introduced to North America from eastern Asia in the mid 1970s to control aphids and other crop-eating insects. They are known for their vigorous reproduction cycle and ability to withstand fairly harsh winters, thus helping them become a predominant species in Canada.

They are slightly larger than the native species, typically 6 – 10 mm long and range in colour from a mustard yellow to a dark reddish orange. They have a varying number of black spots on their wing covers, though some may have no spots. Also the multicoloured Asian beetle has two white oval markings on either side of its head, and usually has an M-marking just behind its head. As with many other insects, their bold colours are a defence, warning birds and other predators that they won’t make a tasty meal. However they do seem to like to bite people!

Throughout the summer, ladybettles feed on soft-bodied insects such as aphids and mealy bugs and when the temperature drops, most species prepare to overwinter on the forest floor, often at the base of trees or under leaves or bark. However, the Asian ladybeetle is attracted to sunny areas, including homes and buildings where they will congregate in the hundreds, even thousands, seeking warmth and a sheltered place to spend the winter. By clustering on the outside walls, many will work their way into the dwelling through gaps in the door and window frames, eaves and openings in the foundation and wall siding. Once inside they become confused, and gather on walls and windows looking for an exit. Many of these die in a short time. But others may find a safe spot to hibernate in the attic or wall openings and emerge from time to time during mild weather.

During the late fall and early spring these lady beetles are either looking for a warm home to hibernate or leaving their homes to find a mate. The Asian beetle can produce several generations a year, and the adult female lays 10-50 tiny yellow eggs near aphid colonies. The larvae are spiny with mostly black and orange stripes.

There are few treatment options to remove them once the Asian ladybeetle has arrived at your house. The best choice is to sweep or vacuum them up and then discard them in a bag. Preventing them from entering the building is the only other method of control. This can be done by improving caulking and weather stripping. As the beetles prefer to congregate on the sunny side of the house, it is best to focus on that side. At present there are no known pest products available for the control of these ladybeetles.

This reference was taken from the Health Canada Pest Management Regulatory Agency. For more pest management information, call 1-800-267-6315.

For more gardening information, phone Master gardener Margaret Inwood at 613-259-3141