Outdoors

How to manage an Asian lady beetle infestation

an asian lady beetle crawls on a leaf Photo by Shutterstock/Paul Reeves Photography

We know what you’re thinking: “Wait, aren’t those ladybugs?” But, in fact, they’re not! Ladybugs and Asian lady beetles (scientific name Harmonia axyridis) might look virtually identical, but the two species are actually very different—especially when it comes to where they like to live come fall and winter. Chances are, if you notice beetles flying inside your home when the weather starts cooling, you’ve got an Asian lady beetle problem, says entomologist and research scientist at the Canadian Museum of Nature, Bob Anderson. “You’ll rarely find native ladybugs in your home,” says Anderson. “They will congregate, but usually in a forest under bark or in a tree, not in your home.” 

Here, we chat with Anderson about why Asian lady beetles like to find shelter in our homes and cottages, whether they’re harmful to humans (and pets!), and how best to get rid of them.

So, ladybugs and Asian lady beetles aren’t the same thing?

They’re not. Unlike our native species, Asian lady beetles were introduced into the United States in the 1900s to help control aphid populations and other plant pests. From there, they travelled around to places like Canada. The two beetles have slight variations in their appearances. Asian lady beetles typically have an “M” shape at the base of the head, right in the middle. On a native ladybug, that space will be solid black.

Why do Asian lady beetles seem to infest homes and cottages around this time of year?

They’re looking for a place to overwinter. They basically need a safe and warm place to hide out until spring. We don’t know why, but they especially like to congregate on reflective surfaces, like the siding of a house or on windows. They’ll get inside through small holes or cracks, and that’s when you’ll see them either crawling or flying around in your home or cottage.

Do they bite?

They do. Technically it’s more of a scrape, but it does result in what looks and feels like a bite. It’ll usually resolve on its own, though. And it’s important to note that Asian lady beetles eat aphids, so they aren’t trying to feed off your blood or anything. 

Aside from the biting, do they pose any other threats to humans or animals?

They’re not going to get into your cupboards and eat your food or anything like other insects might. But you should watch out for what we call reflex bleeding. If you touch or bother Asian lady beetles, they’ll exude this yellowish, really smelly fluid from between the joints on the legs. The scent is unpleasant, but the main issue is that the fluid stains. 

So I shouldn’t swat them with a fly swatter?

Definitely not! Unless you want yellow stains on your walls or furniture.

What’s the best way to get rid of them?

The best method is to suck them up with a vacuum. If they’re in hard-to-reach places, just use a broom to sweep them down to the floor and then vacuum them up. Once you’re done, remove the bag, seal it in a garbage bag so they can’t crawl or fly out, then put that bag outside or in the garage. If you have a central vacuum system, be sure to dispose of the bag from the main unit.  You can use yellow sticky traps to trap the beetles as well, but vacuuming them up is the easiest and quickest way to get rid of them.

What about insecticides?

You might use a household insecticide, like Raid, to knock them down to the ground and disable them, then suck them up with the vacuum. But it’s really not necessary. A broom will do the trick just fine.

Can I do anything to prevent them?

Yes. The main thing is to ensure your cottage or home is well sealed. Check doors and windows for cracks in the caulking around them, and holes in screens. Use any type of acrylic caulking to repair gaps in your window or door seals, and for your screens, you can either replace them or use something like a screen repair tape for a temporary quick fix.

Will Asian lady beetles reproduce in my home or cottage?

No. At this time of the year their reproductive season is finished and they’re just looking to pass the winter. It’s not beneficial for them to breed because it just results in wasted energy. 

How long do Asian lady beetles live?

Most of the ones you find in your house or cottage won’t make it through the winter. That’s because inside, it’s warm. The beetles get confused and think it’s summer again. They’ll fly around looking for food and use up their precious energy stores intended to get them through the winter. If any do survive, say they hunker down between wall cracks or something, you’ll see them again in the springtime trying to get outside for a meal.

Why do Asian lady beetle infestations seem worse in some years?

Similar to all insects, Asian lady beetles go through cycles. Weather and other factors can influence their breeding seasons, making some years more effective than others and resulting in higher or lower populations. Remember that Asian lady beetles primarily eat aphids, which eat plants. If we have a particularly wet and warm summer, for example, that’s going to result in more plant growth, which will mean more aphids, and?

More Asian lady beetles?

You got it.

This interview has been edited and condensed for clarity and length.

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