Before the early 1990s, hundreds of species of native lady beetles or ladybugs dominated North America. Now these natural populations are declining due to competition from an invasive species.
There are a couple theories on how Asian lady beetles made it to North America, but it’s unclear how they established populations. It’s well documented that Asian lady beetles were intentionally imported from Russia, Japan, Korea and from other locations in Asia to be released as part of a USDA biological control program to manage soft-bodied insect pests of trees in the U.S. and Canada. They were selected due to their superiority in controlling tree-feeding aphids and scale insects that native ladybugs are not as effective in controlling. However, these programs were stopped due to consistent failures to recapture the Asian lady beetles. There have also been several reports of Asian lady beetles traveling on ships to various U.S. ports.
Names: Lady beetles, ladybugs and ladybird beetles
Native range: Many parts of the United States. Ladybugs are the state insect of Ohio, Delaware, Massachusetts, New Hampshire, New York and Tennessee.
Description: Ladybugs are beneficial predators that consume aphids, scale insects and other garden pests.
Life cycle: The ladybug’s life cycle from egg to adult takes 4-6 weeks. Adults can live up to 2 years.
Hibernation habits: Ladybugs overwinter clustered in sheltered sites outdoors.
Appearance: They range in size from 0.03-0.7 inches long with oval, dome-shaped bodies. Colors include different shades of red, orange or yellow with or without black spots on their wing covers.
Asian lady beetles
Names: Asian lady beetle, Multicolored Asian lady beetle, Harlequin ladybird and Halloween lady beetle
Native range: Asia
Invasive status: Has also become established in North America, South America, Europe and parts of Africa. It is considered globally invasive. It was recognized in Ohio 29 years ago.
Description: Asian lady beetles are predators that feed on aphids and other soft-bodied insects and scale insects that dwell in trees. They also consume pests that injure commodities such as fruit orchards, Christmas trees, ornamentals, small grains and various agricultural crops.
Life cycle: Their life cycle from egg to adult takes about a month, depending on the weather and availability of food. There are multiple generations per season in Ohio. Adults can live up to 2-3 years.
Hibernation habits: In their native habitat in Asia, Asian lady beetles overwinter in the cracks and crevices of rock cliff faces. This is why they frequently seek out the exteriors of buildings and overwinter in clusters around buildings in North America.
Appearance: Adults are 0.2 to 0.3 inches long. They have a domed, round to oval shape. They come in a variety of colors, including shades of red, orange and yellow, with black spots. The top covering of their middle body section helps distinguish Asian lady beetles from ladybugs. It’s white with a black ‘M’ or ‘W,’ depending on whether you’re viewing the beetle from the front or rear. Older lady Asian lady beetles will appear dull-colored with faded spots, but their ‘M’ or ‘W’ mark typically remains evident.
Environmental impact: Although they are beneficial in controlling pest populations, Asian lady beetles are considered to be a pest by many.
As an invasive species, they lack natural overwintering sites in many locations where they’re found — there are not a lot of rock faces outside of the mountainous regions of the U.S. So they seek shelter indoors, which leads to negative interactions with humans. They have been known to bite and release a yellow-orange body fluid as defense mechanisms. Their bites can’t break human skin; however, their body fluid has a foul odor and can stain surfaces and cause allergic reactions when released on skin. They have been known to be more aggressive than native ladybugs.
They were also considered to be an outdoor nuisance pest in Ohio throughout the 1990s when they congregated in large numbers. They were known to spoil food and drinks at outdoor gatherings in the fall. They would land on people and occasionally crawl in their ears or mouth. If Ohio populations of Asian lady beetles rebounded to their once-large numbers, they could potentially become an outdoor nuisance again.
Asian lady beetles also used to be considered a pest to pumpkins, apples, grapes and raspberries. However, this theory has been debunked since large numbers were observed feeding on these crops in the 1990s. Researchers have found that Asian lady beetles were attracted to crops that had been previously damaged by a plant pest or pathogen. Raspberries are the only crop they feed on directly. Grape products have been affected but inadvertently due to Asian lady beetles being harvested with clusters of grapes and processed into grape juice or wine.
Possibly the greatest environmental impact Asian lady beetles have had is reducing populations of native lady beetle species, not just in North America, but on every continent they’ve inhabited. Declines of native lady beetle populations have been attributed to competition for prey and predation by Asian lady beetles on the eggs, larvae and pupae of native lady beetles.
Asian lady beetle populations can be managed in and around your home by sealing off entry points and applying targeted pesticide treatments in late fall if absolutely necessary. For more information on controlling Asian lady beetles, read How to keep Asian lady beetles out of your house.
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