Lady Beetles

Lady Bug, Lady Bug, Fly Away Home or fly away from my home as many people are now saying. Over the past few years, lady beetles (ladybugs) have been entering homes, sometimes in surprisingly large numbers. Most people like lady beetles but when they start showing up inside the house in the dozens and even sometimes in the hundreds, they start to loose their popularity.

The lady beetle responsible for these home invasions is the Asian Lady Beetle (Harmonia axyridis), also called the Multicoloured Asian Lady Beetle. This beetle is native to eastern Asia where it is a predator of scale and aphid pests on trees. Since the early 1900s, various states in the U.S. have introduced these beetles as natural control agents of certain agricultural pests. Since that time the beetle has increased its population size and is now found in most areas of the United States and parts of Canada. This large and rapid increase is probably due to the abundance of its prey and the apparent lack of natural native enemies. In time, the population size will probably balance out.

Asian lady beetles occur in many colour forms. The adults are oval, convex and about 6 mm long. Colours can range from pale yellow-orange to bright red-orange with or without black spots on the wing covers. The head and area behind the head is straw yellow with dark spots or M-shaped markings. Bright yellow eggs are laid on the underside of leaves. The larvae are often red and black and shaped like tiny alligators.

These beetles are beneficial as they feed on a variety of ornamental, nursery and field crop pests including aphids, scales and psyllids. Adults can consume 90 to 270 aphids per day and larvae 600 to 1200 aphids during their development. Under favourable conditions, their cycle can be completed in about a month and there are multiple generations each year. Adults can live for several years.

Lady beetles do not harm humans or carry diseases. Once in the home, they do not breed or feed (unless you happen to have a lot of aphids on your plants). They enter in the fall to try and hibernate using cracks and crevices that they find on the house exterior. As temperatures warm in late winter and early spring the beetles again become active and often end up inside the house. Like some of the other insects that overwinter in homes, lady beetles are attracted to light and are often found at windows or flying around lights at night.

The best means of control of Asian lady beetles is to try and prevent entry. Sealing, caulking and screening will help reduce entrance points. Once in the house, the vacuum is the best way to remove them. If the temperatures outside are still elow freezing, the beetles will probably not survive if released outside. Squashing or alarming the beetles can cause them to give off a fluid that has an odour and may stain. Generally, pesticide treatment is not recommended or needed for lady beetles. Sometimes when treatments are done for other problems such as cluster flies, this treatment will also reduce the beetle problem. If all else fails, collect them in the spring and release them out in your garden and let them work for you.