The Cute Plague: Preparing for Fall Swarms of Asian Lady Beetles

I am dreading the end of October. That is the usual time for the yearly invasion, the monstrous onslaught of what I’ve come to call “The Cute Plague.” You may laugh at the moniker, but think of a tiny, bright orange bug with black spots. It looks like the domestic ladybug, but it is an imposter from Asia. It is the Asian Lady Beetle, and I am deluged with thousands of these cute but annoying little buggers every winter.

How do you tell them apart from the domestic ladybug? After all, both bugs are small, round, orange and have spots, right? Well, not exactly. The Asian Lady Beetle (also called the Multicolored Asian Lady Beetle) can be a few shades of orange, from bright (nearly red) to washed-out, and it may or may not have spots. One obvious mark that pegs it right away is a small “M” or “W” shaped mark behind its pronotum (the area just behind its head). If you see this, it is an Asian Lady Beetle.

What are these beetles good for, anyway?

Asian Lady Beetles were introduced into this country many years ago to fight the scourge of aphids (fruit lice), which suck the sap out of crop plants like pecans and soybeans. In 1916, they were introduced in California, and in 1978-82, the USDA introduced them in the southern states of Georgia, Mississippi and Louisiana, as well as Washington State. The latter introduction was specifically for the purpose of controlling the pecan aphid, but they would also feed on rose, apple, myrtle, poplar and conifer aphids as well. As the aphid population dwindles in the fall, the beetles might be seen feeding on fruits to supplement their diets. Although the Asian Lady Beetle is classed as a beneficial insect, it does have its annoying drawbacks, as I’ve discovered.

Good bugs gone bad: the Dark Side of our beetle friends

If an Asian Lady Beetle lands on you, it may pinch or bite your skin, which is, naturally, quite unpleasant. They do not break the skin, however, and so they are not a disease vector. The irritation caused by the beetles can cause rashes and reddened areas on the skin, and some people do develop allergic dermatitis-type reactions to the beetles. It also exudes a foul-smelling yellow/orange-ish liquid from its joints when it is disturbed. This is called “reflex bleeding” and is a defensive measure. This liquid does stain surfaces, though, and if you don’t clean your surfaces of the exudates of the Asian Lady Beetle, the chemical signaling agents will draw them in greater numbers.

The tendency of the beetles to switch from aphids to fruit in the fall has also affected winemakers adversely, as beetles’ attentions impart an unpleasant taste to wines. They are often caught up in processing along with the grapes and thus crushed into the wine mass.

Fall invasion of homes and other structures

As winter draws close, the beetles would seek out overwintering spots, such as cracks and crevices in rocks or mountains in Asia. Here in the US, they often seek out houses and other protected structures with hiding places. That means they will find their way behind vinyl siding, through cracks in walls or foundations or through damaged window screens or frames and through gaps under and around doors. Log cabins are the worst, because there are so many chinks and places to hide. This is one time of year I am not happy to be living in one.

The Asian Lady Beetle usually swarms on the first relatively warm, sunny day after the first killing freeze. In Tennessee, this usually happens around the last week of October. Usually the temperature has to get to at least 50 degrees Fahrenheit in the daytime to stir the bugs to action, and often the beetles will swarm for several days in a row. They are attracted by light, preferring light-colored walls and western or southern facing walls that get plentiful sunshine. Even though I have a dark cedar cabin, the bugs still swarm to it, so dark surfaces are by no means safe from them.

The swarm density varies from year to year. In drought years, when there are fewer surviving plants to support the aphid population, the beetles are also less abundant. Often you can predict the severity of the beetle swarm by the quality of the summer, i.e., whether it rained sufficiently, how well crops grew, the number of temperate days, etc. In light years, I would count less than 30-50 beetles in the house on any given day. In heavy years, they can number in the thousands, especially before I realized how they were getting in.

Ways to prevent beetles from entering your home

Caulk around your house, especially cracks next to window. Repair or replace any damaged window screens. Weatherstrip windows and doors and add a bottom “sweep” to doors that open to the outside. Seal around openings to the house, such as outside faucets, dryer vent, wiring that comes into the house through holes, etc. This can be done with caulk, cement or steel wool or copper mesh. Larger openings can be effectively sealed not only against the bugs but against mice and rats by using the mesh in conjunction with caulking or expandable foam. Soak the outer western and southern walls in a contact insecticide. Most sites recommend pyrethrin-based insecticides, but they are not as effective as the organophosphate malathion. However, there are many dangers in using organophosphates, as they can be harmful to pets and humans. If you live in a wood cabin like I do, be sure there are no gaps in the logs themselves through which the beetles can slip into the house. I have personally found cracks that show daylight, and I caulk these over whenever I find them.

How to control Asian Lady Beetles if they get into your house

The first item is a don’t: it is not recommended to use pesticides inside the house for controlling the beetles. Since the bugs work themselves into cracks and crevices, the pesticides, which will only work if they directly contact the insect, will not be effective. Also, in the winter conditions, a closed house and recirculated, heated air will add to the danger of breathing in the poison. Minimize the light sources inside the house, or use concentrated light (or black light) in conjunction with glue traps to collect the beetles and either return them outside or exterminate them. I suggest that, if you experience a significant invasion, you would be better off removing any lampshades that you want to keep. The beetles are notorious for staining lampshades. Vacuum the beetles from their hiding places and take the bag outside. You can then dispose of the bag or open it far from the house to set them free. It is best to do this on a sunny, relatively warm day, so they don’t end up right back at your house! Some people have noted successes with repelling Asian Lady Beetles using white sage, bundled and smoldered to produce smoke. This is reputed to drive off the beetles from inside the house. You can also burn the sage outdoors on swarming days to drive them away. There are also sage-based skin applied bug repellents that are reputed to be effective for personal use. Keep walls and windows clean, as the beetles give off a scent that draws more of them to a spot they’ve decided is good for overwintering. This can cut down on the severity of the infestation.

Final Note: It is best not to let the dead beetles collect in the corners of your house if you can help it. Their carcasses can attract other bugs that will cause damage, such as the carpet beetle, which will destroy wool fabrics and consume grains and pet foods. So, be on the lookout, and nip these cute flying nuisances in the bud if they try to make themselves welcome in your home this Fall.

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