- One species of lady beetle, the multicolored Asian lady beetle (MALB) has become a nuisance in Minnesota.
- They cluster around buildings in large numbers during fall in search of protected sites for the winter
- Control measures should only be used to prevent entry of Asian lady beetles indoors.
- Other lady beetle species feed on aphids and other soft-bodied insects that can damage plants in agricultural crops, gardens and landscapes.
- These are beneficial insects to farmers and gardeners.
Multicolored Asian lady beetle, Harmonia axyridis (Pallas) is also known as Asian lady beetle, Halloween lady beetle, and Japanese lady beetle.
How to identify Asian lady beetles
The multicolored Asian lady beetle looks very similar to other lady beetles but is generally larger, about 1/3-inch long.
- It can be seen in a range of colors, ranging from orange to yellow to red or even (rarely) black.
- This beetle typically has 19 black spots which can vary in appearance from well-defined to no more than faint traces on its wing covers.
- These lady beetles may also have fewer than 19 spots and some may have no spots at all.
- Look for the clear black 'M'-shaped marking behind its head, to correctly identify the multicolored Asian lady beetles.
- The 'M' can look thick, thin or even broken in appearance.
- The immature larvae are alligator-like, and appear similar to other lady beetle larvae.
Larvae are blue to black with two orange stripes, and rows of small, spines on their bodies.
Asian lady beetle as a household pest
Multicolored Asian lady beetles can be a nuisance when they occur in large numbers inside homes.
- They do not infest wood, destroy fabrics, eat food or damage other property.
- These lady beetles cannot sting and do not carry disease.
Some concerns with multicolored Asian lady beetles are:
- Some can bite hard enough to break human skin, causing minor, short-lived discomfort. These bites happen when the beetles are searching for moisture or food.
- They can secrete a strong-smelling yellowish liquid from the joints of their legs. This liquid can stain light colored surfaces.
- Exposure to dead lady beetles in buildings can cause allergic reactions in some people.
Asian lady beetle as a garden pest
Asian lady beetles are common in wooded areas, agriculture fields and home gardens. When they run out of their preferred food source (aphids), these lady beetles fly to another food source, often fall-ripening fruit such as grapes, apples and fall raspberries.
- These insects only infest apples that already have wounds, such as holes made by birds or other insects.
- Ripe or nearly-ripe apples may be seen with fairly large cavities in them and a number of lady beetles inside eating the apple’s flesh.
- Picking up fallen apples and removing damaged apples still on the tree will help reduce the number of lady beetles on apple trees.
VedgEdge has more information about Asian lady beetle as a crop and garden pest.
How to protect your homes from lady beetles
Preventing entry is the most effective step.
- Check the outside of your home for spaces and cracks that may allow insects easy entry.
- Lady beetles can fit through openings as small as 1/8 inch in size.
- Make any necessary repairs by the end of September.
- Seal cracks and spaces around doors, windows and fascia boards. Check for gaps and cracks where different materials meet, such as brick and wood siding. Seal cracks with caulk, such as silicone, elastomeric latex or silicone/acrylic.
- Seal areas where cable TV wires, phone lines, and other utility wires and pipes, outdoor facets, dryer vents and similar objects enter buildings.
- Seal with caulk or for larger spaces use polyurethane expandable spray foam, steel wool, copper mesh or other appropriate sealant.
- Repair or replace damaged window and door screens.
- Repair or replace damaged screens in roof and soffit vents, and in bathroom and kitchen fans.
- Install door sweeps or thresholds to all exterior entry doors. Install a rubber seal along the bottom of garage doors.
- This will not eliminate all lady beetles but it will reduce the number entering buildings.
Use a residual insecticide barrier to limit the entry of lady beetles. Apply in late September or early October, before insects begin to enter buildings. Some examples of effective active ingredients in pesticides are:
Apply around doors, windows and roof lines. Pay particular attention to the south and west sides where the insects are most numerous.
You may want to contact a structural pest management service.
CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.
When lady beetles are seen indoors
Spraying pesticide sprays indoors is not effective. Once lady beetles move into wall voids in the fall there is no way to prevent them from emerging later during winter or spring.
When you find lady beetles in your home, remove them with a vacuum.
Lady beetles are not automatically killed when they are vacuumed.
Change the bag frequently to prevent lady beetles from escaping and to minimize their smell.
You may use a knee high nylon stocking that has been inserted into the extension hose and secured with a rubber band. As you vacuum, the lady beetles are captured in the stocking.
- Remove the stocking after vacuuming, so the captured beetles won't escape.
- Use the rubber band to close the stocking and throw it away.
- The stocking may also be reused after discarding the contents.
More information about Asian lady beetles
In Asia, multicolored Asian lady beetles feed primarily on aphids found in trees.
In the U.S., they feed on aphids not only in trees but also in agricultural crops and gardens.
This beetle is an important predator of soybean aphids, a serious pest of soybeans in Minnesota and other Midwest states.
In Asia, these insects fly to cliffs each fall where they live through the winter in large numbers. When such areas are unavailable in the U.S., beetles look for sunny sides of tall or prominent buildings during fall.
- Buildings with dark and light contrast are attractive to lady beetles.
- Buildings close to wooded areas are more likely to have Asian lady beetles than buildings in open areas.
Lady beetles fly to buildings between late September and late October in Minnesota. This is the time when temperatures are above 65 F before the freezing temperatures set in.
- Lady beetles crawl into cracks and gaps around windows, doors, roof lines and other openings.
- Some continue to move inside until they reach the living areas of homes where they soon die.
- Others find suitable sites to spend the winter inside wall voids, attics and other areas. Large living masses of insects can sometimes be seen in such sites.
Mild, sunny winter days can wake these dormant insects. All lady beetles become active at different time, depending on how much warmth reaches their location.
Then they follow the warmth into the home's living quarters. Once there, they move towards windows and other sunny areas. During spring, they try to move outdoors but many remain trapped indoors.
Multicolored Asian lady beetles do not reproduce indoors. All the lady beetles seen inside during winter and spring must have entered buildings the previous fall.
Reviewed in 2018