The Multicolored Asian Lady Beetle (MALB)
Pest expert Matthew S. Hess, CEO, Four Seasons Pest Solutions, Inc.
The multicolored Asian lady beetle (Harmonia axyridis (AXE-A-REE-DEES), originally native to Asia, has been present in the United States for over a century. First introduced in 1916 in California as part of biological pest control efforts aimed at managing aphid populations, their presence has grown significantly since then. Although their introduction dates back to the early 20th century, widespread awareness and encounters with the beetle did not occur until after the 1990s.
During the 1970s and 1980s, Harmonia axyridis was intentionally released in several states bordering the Gulf of Mexico (now the Gulf of America) and the Atlantic Coast. By 1988, the first significant records of established populations were documented in New Orleans, Louisiana. Remarkably, within a mere five years, evidence of overwintering populations was confirmed. By 1994, the multicolored Asian lady beetle had extended its range across North America, from the southern tip of Florida up into Canada, and from the East Coast to the West Coast (Bahlai et al., 2015; Michaud, 2002). Much of the way the multicolored Asian lady beetle was introduced into North America remains a controversy with credible sources documenting both intentional and unintentional introduction.
Success or Failure?
MALB is a significant predator, particularly skilled at feeding on soft-bodied insects like aphids, a variety of other prey that native lady beetle species consume, and native lady beetle eggs, larvae, and pupae. This ability makes the MALB an important player in crop pest control, as it can effectively reduce certain crop pest populations more efficiently than our native lady beetles. In fact, studies conducted in England in 2011 demonstrated that the MALB’s impact on prey was so considerable that it led to a nearly 50% decline in native lady beetle species, a downside to their success. However, it also makes them a key culprit in native species’ decline.
Besides their negative impact on native lady beetle species, the MALB’s success was also paralleled by yet another downside: they quickly became a pest in commercial buildings and residential areas. By the time they were noticed congregating on homes and buildings, they had already begun to enter indoors to overwinter, and the general population despised them. By the mid-1990s, the MALB had established itself as a pest, prompting great efforts to reduce its population numbers and bring them under control.
Multicolored Asian lady beetles feed on several soft-bodied insects, making them beneficial to the agricultural world but a threat to native species.
Adult Multicolored Asian Lady Beetle Identification
The term “multicolored” aptly describes the diverse array of color variations exhibited by the multicolored Asian Lady Beetle. These variations can include hues such as orange, yellow, and red, each with a range of shades. Additionally, some individuals may display distinct black spots on their elytra, which can differ in color, size, intensity, and quantity, with 19 spots frequently observed.
Similar to native lady beetle species, adult Asian lady beetles measure approximately ¼ inch in length. Their wing covers contribute to a convex, (dome-like) shape on the dorsal side, while the ventral surface remains flat, akin to the larval stage. Viewed from above, MALBs exhibit a rounded profile, epitomizing the quintessential characteristics of a beetle.
A key identifying feature utilized by pest professionals is the presence of a white pronotum, marked by a distinctively shaped black “W” or “M,” depending on whether the beetle is viewed from the head or abdomen.
MALBs are notably recognized by pest professionals for their unique overwintering behavior, as they tend to congregate in large clusters of adults within man-made structures and dwellings. This behavior contrasts with that of native lady beetle species, which may also cluster but have not been documented to seek refuge in human-made environments. This distinctive trait is crucial for classifying MALBs as pests, in contrast to native species deemed beneficial.
MALB have multiple color variations.
MALB may loose their spots and sheen as they age. Some may have more or less spots with 19 being most common.
MALB Life Cycle
From egg to adult, the life cycle of the Multicolored Asian lady Beetle encompasses four stages of complete metamorphosis: egg, larva, pupa, and adult. The entire process takes between 15 and 25 days (some observations document 30 days) and depends upon food supplies and temperatures.
Once an adult, the Asian Lady Beetle can live a surprising 2 to 3 years. As they age, the older adults become somewhat dull-colored and may lose both their spots and sheen. Within a single season, including all overwintering clusters, multiple generations will be present.
Multicolored Asian lady beetles undergo complete metamorphosis.
MALB larvae molt four times before pupating.
MALB Eggs
The oval-shaped eggs of the MALB are yellow and are laid in clusters of 20 near food sources. They are attached to the undersides of leaves, sticks, and other naturally occurring materials. Depending on the weather, the eggs will hatch into larvae within 3 to 5 days.
Harmonia axyridis lay their eggs in clusters on the underside of leaves, twigs, and similar items.
MALB Larvae
In contrast to the classic dome-shaped morphology of adult beetles, the larvae exhibit a distinctive alligator-like shape, characterized by an elongated and flattened body that is adorned with small, flexible spines that do not sting. Throughout the subsequent 12 to 14 days, the larvae will experience four distinct molts, with each stage resulting in an increase in size. These larvae possess adaptations that enable them to navigate their environment with remarkable speed and efficiency while foraging for sustenance. Following their final molt, the larvae transition into the pupal stage, securely attaching themselves in locations that are often reminiscent of the sites where the eggs were originally laid.
MALB larvae are alligator-shaped and have non-stinging spines on their backs.
MALB Pupae
Once fixed to their pupal habitat, they will typically spend 5 to 6 days undergoing preparatory changes before emerging as adults. During this pupal stage, the MALB reaches a size comparable to that of the fully developed adult and exhibits two longitudinal rows of parallel black spots, along with two distinct body segments.
The MALB pupae reattach themselves to the underside of leaves and similar debris to pupate. They are about the same size as an adult.
Asian Lady Beetle Habits, Benefits, and Preservation
The Multi-colored Asian Lady Beetle is not without its challenges, many of which have direct implications for human populations. Nevertheless, despite its classification as a non-native and invasive species, the MALB also plays a crucial role as a beneficial insect for agricultural practitioners, including those in farming, horticulture, and ornamental landscaping. The contributions of MALBs to pest control significantly mitigate the damage inflicted by various agricultural pests, thus preventing losses that can amount to millions of dollars annually across a wide array of essential commodities, such as fruits, vegetables, ornamental plants, Christmas trees, grains, and more.
Consequently, the Asian Lady Beetle is a vital component of our agricultural economy and the overall well-being of our nation and its populace. It is imperative, therefore, to establish a sustainable ecological balance that addresses pest issues in residential and commercial environments while simultaneously preserving the MALB’s valuable role in agriculture.
Negative Impacts of the MALB
The MALB does play a vital role in the agricultural industry and positively impacts our economy but there are important nuisances that arise from their presence. Of their negative behaviors, the two most important are their impact on soft fruit crops and our native lady beetle populations.
Generally, there are three main categories that define their negative behavioral patterns. These are:
- Their impact on fruit and fruit products
- Their competition with native lady beetles
- Structural infestations
MALB’s Impact on Fruit and Fruit Products
Asian lady beetles are capable of infesting fruit crops, contaminating fruit and fruit juice, and injuring fruit. In winemaking, MALB can have a devastating effect. Their blood contains bitter alkaloids that are used in their defense. These alkaloids are released when crushed. As few as 1500 beetles in a ton of grapes can render wine useless. Besides grapes, MALB may infest several other soft-bodied fruits including:
- Peaches
- Raspberries
- Blackberries
- Mulberries
- and several others.
Although fruit injury has been documented, most injured fruit has been proven to have had previous damage by other sources prior to the MALB feeding.
Asian Lady Beetles vs Native Lady Beetles
The presence of the Multicolored Asian Lady Beetle poses significant challenges to native lady beetle populations. Both MALB and native lady beetles predominantly consume similar food resources, leading to competition that can result in a scarcity of food supply. Native species, often less numerous, typically struggle to rebound from population declines compared to the more prolific MALB.
Asian Lady Beetles also exhibits aggressive predation behaviors, directly targeting the eggs, larvae, and pupae of native lady beetles. This interspecific competition extends to overwintering sites as well, where MALB’s larger populations can outcompete native species for essential winter harborage. Consequently, native lady beetles may face increased difficulties in locating adequate shelter, resulting in higher mortality rates during the harsh winter months.
The MALB’s biological resilience enhances its survival rate in adverse conditions as well. This adaptation ensures that they not only endure environmental stresses better than their native counterparts but also exploit changing habitats more effectively.
Beyond dietary competition, the Multicolored Asian Lady Beetle may also be a vector for microsporidian parasites, which can significantly impair the health and reproductive capabilities of native lady beetle populations. Such parasitic infections create further obstacles, exacerbating the challenges faced by indigenous species and threatening their long-term viability.
The competitive dynamics created by MALB profoundly impact native lady beetle populations, highlighting the importance of monitoring and potentially managing these invasive species to preserve biodiversity.
Indoor Infestations and Outdoor Nuisance
As winter approaches, the Multicolored Asian Lady Beetle begins its search for shelter shortly after the first freeze or drop in temperature to near-freezing. These beetles then wait for a warm day, typically around 65 degrees Fahrenheit, to commence their quest for a suitable winter refuge… that just might be in your home!
During this search, it’s not uncommon to see these beetles congregating in large numbers on the exterior of buildings. Their affinity for high-contrast areas in nature (rocky cliffs) makes homes, despite being far from that natural habitat, appear inviting. Buildings with contrasting colors, such as siding, roofing, or shutters, can mimic the features of their natural environment, leading the beetles to mistake them for the crevices they would typically seek in rocky cliffs and mountain sides.
The prime time for spotting MALB on buildings is from mid-October to early November. As cold-blooded creatures, they require shelter from low temperatures to survive the winter. Contrary to popular belief, however, they are not in search of warm areas. If the temperatures are too warm, MALB can’t enter true hibernation, which can lead to their death. Many homeowners find dead beetles indoors during the winter months because the insects attempted to hibernate in spaces that were too warm to allow for a proper hibernation cycle.
To conserve their energy, MALB slows its metabolism, relying on stored fat reserves to endure the cold months. They often form large clusters to maintain warmth, rotating positions within the group to ensure an even distribution of heat. When temperatures are too warm, their metabolism cannot slow, and their reserves are quickly consumed, leaving them to starve to death. This leaves homeowners to find their dead carcasses around window seals and on floors or various similar locations throughout the winter into spring. If the beetles survive hibernation within your home until the end of winter, they will emerge to return to nature where they will begin the life cycle over again.
Common areas for the Asian Lady Beetle to overwinter include:
- Leaf litter and wood mulch
- Wood and wood structures (such as landscaping and firewood)
- Under roof shingles and metal roofing
- Under siding
- In soffits
- Attics
- Basements
- Crawlspaces
- Around windows and window frames
- Other undisturbed areas
In homes where cracks and crevices exist, MALB can accidentally enter living spaces, leading to a growing nuisance each year. Even though they may be searching for a way out, the lack of resources indoors is detrimental to their survival.
These accidental invaders can cause significant annoyance, even after they die. Therefore, it is essential for homeowners to implement both pest control and exclusion strategies to manage and mitigate MALB infestations effectively.
Damages Caused by MALB
While the MALB does not cause structural damage to homes and buildings, their large populations can lead to significant aesthetic issues both indoors and outdoors. This can result in damaged furnishings, spoilage of food and supplies, allergic reactions, potential bites to humans, and unpleasant odors inside the home.
The aesthetic damage, furniture loss, and foul smells are primarily due to their natural defense mechanism known as “reflex bleeding.” This process involves the secretion of a yellowish-orange fluid from the joint between their femur and tibial leg segments.
Most often, damage to food and supplies, allergic reactions, and bites are the result of large groups of these beetles accidentally making their way indoors. To reduce this, adequate management strategies should be implemented for their control.
Multicolored Asian Lady Beetle Management Strategies
There are several management strategies that can be implemented to reduce the likelihood of Multicolored Asian Lady Beetle infestation if not completely prevent it.
Excluding the MALB
Among the various strategies used to reduce or eliminate the Multicolored Asian Lady Beetle from entering buildings, prevention has proven to be the most effective. This prevention typically involves pest exclusion, which is the process of sealing all potential entry points to block access for pests. Once the MALB is unable to enter a structure, they will need to relocate to a different area where they can safely hibernate for the winter. To effectively prevent their entry, pest exclusion should be completed before the first freeze, generally before mid-October.
To properly exclude MALB from structures, here are a few key factors to consider:
- Seal all cracks and gaps down to 1/8 inch with quality sealant
- Check siding, utility penetrations, doors, windows, soffit, roof lines, and vents for cracks, gaps, holes, and crevices.
- Inspect doors and windows for gaps and cracks and repair with proper seals
- Install door sweeps on the bottoms of doors
- Check out our other blogs and vlogs on pest exclusion
Trapping the Asain Lady Beetle
Trapping MALB is generally challenging and often ineffective on its own. However, it can be a useful component of a comprehensive control program once the beetles have already infested a structure. The most common and effective traps for targeting these pests are black light or ultraviolet flying insect traps, also known as fly light traps. These traps use ultraviolet lights to attract the insects and feature a sticky trap (glue board) to capture them. For those who enjoy DIY projects, instructions on how to build an effective trap can be found here: https://www.ars.usda.gov/is/br/lbeetle/001030.trap.pdf.
Mechanical Removal of the Multicolored Asian Lady Beetle
Pest removal can take many forms, ranging from sweeping up dead insects to using a vacuum to manage live ones. It is important to understand that removal primarily focuses on cleaning up an infestation rather than completely eradicating it. In most cases, homeowners will not have direct access to the MALB’s winter colony, which means live bugs may still emerge during their hibernation period.
If you decide to use a vacuum for either live or dead insects, it’s advisable to use a shop vacuum equipped with a HEPA filter. Unlike standard vacuum cleaners, shop vacs allow the vacuumed materials to bypass the fan, which serves a critical purpose. MALBs release unpleasant odors when crushed, and their fragmented body parts can become airborne, potentially spreading allergens into the environment. Therefore, using the appropriate equipment is essential for effective and safe pest management.
DIY Pest Control
To help reduce the population of multicolored Asian lady beetles, DIY pest control can be an effective strategy alongside the previously noted methods. Once a population has established itself, pesticide treatment may be the most effective way to manage the infestation. When using pesticides, aways follow the manufacturer’s label instructions and wear the appropriate personal protective equipment (PPE). Remember to ALWAYS READ THE LABEL BEFORE USING PESTICIDES! In Kentucky, adhering to the label is a legal requirement, meaning that any violation of these instructions is illegal and dangerous. The label is designed to ensure safety for you, bystanders, pets, and the environment.
If you choose DIY pest control, focus on treating the exterior of your home, as this is where MALB typically enters. Interior treatments can only kill pests as they emerge from hibernation and the goal is to prevent hibernation within your home or other structure. The ideal time for exterior application is from mid-September to late October; be careful not to treat too early or too late as either will render the treatment useless.
A long-lasting, non-repellant insecticide can provide excellent results (note that many effective options may not be available to homeowners) and can be used for pre-entry control. Always consult the pesticide label to determine the best application areas for your target pest.
Some areas of treatment may include:
- Eaves
- Attic, eave, soffit, and roof vents
- Cracks and Crevices
- Roof line
- Exterior walls
- Doors
- Windows
- Siding corner trim and J-channels
- And more
Refrain from using any “bug bombs” or “foggers” in your treatment regimen. These are not only potentially dangerous but virtually useless against most pests, especially MALB. If you’re unsure what to do, what to use, or how to treat, it’s best to consult a licensed pest control professional to perform the proper treatments necessary to prevent MALB from entering your home.
When performing DIY treatments, there are some important factors to consider:
- Always read and follow the label on any insecticides
- Wear the proper PPE when applying pesticides
- Use proper application equipment
- Avoid applying pesticide under strong winds
- Be sure to make application to areas where pest can enter or harbor
Remember, pesticide control of Multicolored Asian Lady Beetles is temporary at best and should be used in conjunction with a complete control program that includes exclusion measures that stop entry.
Professional Pest Control
When insecticides are necessary, effectively managing the Multicolored Asian Lady Beetle requires expertise that only pest management professionals typically possess. These professionals come equipped with years of training, experience, and knowledge, along with effective treatment methods. Their expertise is crucial not only for successfully managing the MALB but also for ensuring your health and safety.
While do-it-yourself projects may initially appear to be a more economical option, they often end up being more costly in terms of both products used and time spent. Hiring qualified professionals can ultimately save you money, reduce stress, and prevent a winter filled with multicolored Asian lady beetles invading your home!
What Four Seasons Pest Solutions Can Do For You
Here at Four Seasons Pest Solutions, we have the ability to follow through with a complete control plan that is aimed at permanently eliminating MALB from your structure. This can include any or all aspects of the noted methods and strategies. However, for those who cannot afford complete elimination programs, we offer short-term control efforts as well. These are aimed at preventing the entry of MALB on a year-to-year basis. Ultimately, we have a control plan for every budget that can be implemented to reduce or eliminate your MALB infestation today!
