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When Lady Beetles Wear Out Their Welcome

Ladybugs have always been looked upon as beneficial insects, worthy of protection. Their presence is often a sign of good luck because they feed on many serious plant pests and, in some cases, they have completely controlled certain pest outbreaks. Recently, however, homeowners have had to reassess ladybug's favorable reputation. When faced with the emergence of literally thousands of lady beetles inside a home or garage during late winter, the words beneficial, conservation and protection seem to be the last that come to mind. Pest control operators and Extension university personnel have also been sent reeling. How can these insects not be a pest when complaints come in by the bucket load and accounts are canceled because of lack of control? What is the explanation for this new problem? What is to be expected? What can be done?

Asian Lady Beetle
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Before we begin to answer these questions, it is important to understand the origin of this particular problem. Many different species of ladybugs occur throughout the world and, although they have many characteristics in common, they are not all identical.

For example, all ladybugs feed on small insects such as aphids or scales that they capture on plants. The fact that they feed on these potential pests is why ladybugs are considered beneficial. Protecting them or even purchasing and releasing certain species in high numbers to augment natural populations will enhance existing biological control processes. However, it must be pointed out that although general body shape is usually similar, there are vast differences in size and coloration between ladybug species. Even more important is the fact that subtle differences in behavior also occur between species. In fact, it is one such behavioral difference that makes one ladybug, commonly called the Asian lady beetle, a pest as well as a beneficial insect. This peculiarity is in the form of an unusual over-wintering habit. Asian lady beetles congregate in large numbers during the late fall rather than disperse to overwinter individually under bark or in leaf litter, as do most lady beetles.

Asian lady beetles prefer to cluster on the sides of homes and other buildings and eventually work their way into the building through small cracks or crevices, or natural breaks in the window panes, door jambs or foundation cracks as the temperatures decrease. Once inside the building, they essentially laze about in a hibernation-like mode, neither eating or moving much until the first warm days of late winter or early spring. At that time, the beetles seem to come to life again and begin crawling about. It is at this time that most homeowners really notice their company. A few found here or there might be tolerable, especially in light of their beneficial reputation out of doors; but when clusters of several hundred to thousands appear in a living room, bedroom, or kitchen it is hard not to grumble.

Why my home?
Researchers have indicated that this particular beetle spends a majority of its active life feeding high in trees. It, no doubt, protects the trees from insect pests while there, however, in late fall when it begins to migrate, it flies well above the tree tops until it zeros in on a preferred aggregation site below. Beetles tend to be attracted to lighter colored buildings, and especially to those that are illuminated by the sun. For this reason, beetles usually choose the southwest facing sides of light-colored buildings. Darker colors, or buildings in the shade are less likely to experience problems. Once several beetles have settled on a suitable site, they presumably release a chemical cue which attracts even more beetles.

Good news and bad news:
The good news is that when Asian lady beetles occur in the home, they are really only a 'pest by their presence.' This is because they do not feed on or damage anything in the home. They do not bite people or pets, do not infest stored food and they do not destroy household furnishings. Their presence is simply a nuisance that most people would rather do without. After spending the winter months tucked away in a wall void or other secluded place, they have simply forgotten how they got in. When they become active in the late winter, they often find themselves inside the home rather than outside. At this time, they are merely looking for a way to escape to the out-of-doors. The best suggestion is to help them in their quest by sweeping them up and depositing them outside if possible. Vacuuming also will work where there are a lot of them, however, be sure to empty the vacuum bag after each time because live beetles can easily find their way out of a vacuum left in the closet.

The bad news is that the beetles seldom all become active at exactly the same time. This reawakening may take place over several weeks, depending on temperatures and the size of the population. Removing those that become active every day can become a real chore, especially where populations are high. It may seem like there is an endless population or that they are somehow breeding in the home. Rest assured that they will not and cannot breed inside the home. Sometimes, chemicals can be used to assist homeowners in removing Asian lady beetles. Using chemical sprays or 'fogs' labeled for inside the home will kill Asian lady beetles. However, the dead beetles will still need to be removed after they die in conspicuous places. This job can be nearly as disagreeable as removing live beetles. If populations are inside wall voids, false ceilings or other inaccessible places, chemical control becomes difficult. Chemicals sprayed or released inside the home will not penetrate these or other secret hiding places. Asian lady beetles in a home will only die after they become active, enter the living areas and contact the chemical residues. In most circumstances, a combination of several control methods is the best answer to Asian lady beetle problems.

Physically removing the beetles, as described above with a vacuum or sweeping them out, is always a good control method. Sealing them out by caulking cracks and crevices, utility service openings, fixing broken window screens and door jambs, plugging cracks in the foundation or roof, as well as other similar exclusion type activities, will help prevent the lady beetles from entering in the first place. Using pesticides as a perimeter treatment during late fall will also help prevent beetles from getting into the home initially. Use materials which will leave a long-lasting residual. Wettable powders, micro-encapsulated and suspended concentrate formulations seem to work best.

--from Plants and Pests, Purdue University 
This page is updated monthly.
Revised:  November 06, 2017