[Seasonal Pest] Luck be a Lady Beetle

Pest control firms from coast to coast will soon be taking calls about ladybugs entering buildings. There are more than 4,000 species of lady beetles worldwide. Almost all are considered beneficial since they feed on plant pests and spend their entire lifetime outdoors, overwintering as adults beneath leaves, bark and debris. One species of lady beetle, Harmonia axyridis, can be a nuisance however, when they fly to buildings in search of overwintering sites and end up indoors. Once inside they crawl about on windows, walls, etc., often emitting a noxious odor and yellowish staining fluid before dying.

While some householders consider the beetles simply a nuisance, others find them intolerable, impacting their quality of life. Lady beetles entering buildings can be especially troubling in high-clean environments such as hospitals and food plants where insects of any kind are contaminants.

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Catnip Compound Curbs Lady Beetles

At certain times of the year, the multi-colored Asian lady beetle, Harmonia axyridis, comes inside – sometimes in large swarms – to escape the cold. It’s an unwelcome guest for your customers because when it feels threatened, it releases a non-toxic yellow liquid that smells foul and produces stains. But in one study, researchers found that almost all adult male and female lady beetles turned away or otherwise tried to avoid the catnip compound nepetalactone – a substance that also shows promise for repelling some cockroaches, flies, termites and mosquitoes.

These findings could lead to a combined "push-pull" control method, which would use repellents to discourage lady beetles from entering buildings and traps to lure and capture the insects.

(Source: Agricultural Research/February 2010)

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WHERE DID THEY COME FROM? The Asian lady beetle, Harmonia axyridis (Pallas), is relatively new to this country. The beetle is native to Asia (e.g., China, Russia, Korea, Japan), where it dwells in trees and fields, preying on aphids and scale insects. The first field populations in the United States were found in Louisiana in 1988. Since then the beetle has expanded its range to include much of the U.S. and parts of Canada.

During the 1960s to 1990s, the U.S. Department of Agriculture attempted to establish the Asian lady beetle to control agricultural pests, especially of pecans and apples. Large numbers of the beetles were released in several states including Georgia, South Carolina, Louisiana, Mississippi, California, Washington, Pennsylvania, Connecticut and Maryland. Some scientists believe that current infestations in the U.S. originated not from these intentional releases, but from beetles accidentally transported into New Orleans, years before, on a freighter from Japan.

DESCRIPTION & HABITS. Adult Asian lady beetles are oval, convex and about 1/4-inch long. Their color can vary widely from tan to orange to red. They often have several black spots on the wing covers, although on some beetles the spots may be indistinct or entirely absent. Multi-spotted individuals tend to be females while those with few or no spots tend to be males. Most beetles have a small, dark "M"- or "W"-shaped marking on the whitish area behind the head.

Eggs are yellow, oval, and typically laid in clusters on the undersides of leaves. The immatures (larvae) are often orange and black and shaped somewhat like tiny alligators. Larvae complete their development on plants where their primary food (aphids) is abundant. The non-mobile pupal stage remains attached to vegetation by its molted skin, but occasionally may be found clinging to exterior walls of buildings. The average time from egg to adult is about one month and there are multiple generations per year. Individual beetles can live up to three years.

At present, Asian lady beetles appear to have few natural enemies. As a defense against predators, the beetles secrete a foul smelling yellowish fluid from their leg joints when disturbed (see photo, page 84). Some mortality occurs at sub-freezing temperatures, although survival is enhanced within buildings and other protected locations if adequate moisture or humidity is available.

In its native land, the Asian lady beetle is mainly tree-dwelling, living in forests and orchards. In Japan, it is also abundant in soybean fields. In the U.S., the beetles inhabit ornamental and agricultural crops, including roses, corn, soybeans, alfalfa and tobacco. During spring and summer, larvae and adults feed mainly on aphids, consuming hundreds per day. For reasons that are not entirely clear, it does not have the same strong tendency to invade buildings in Asia as it does in the United States.

BUILDING INFESTATIONS. As autumn approaches, the adult beetles leave their summer feeding sites in yards, fields and forests for protected places to spend the winter. Unfortunately, homes and buildings are one such location. Swarms of lady beetles typically fly to buildings in September though November depending on locale and weather conditions. Beetle flights are heaviest on sunny days following a period of cooler weather, when temperatures return to at least the mid-60s. Consequently, most flight activity occurs in the afternoon and may vary in intensity from one day to the next.

Studies have shown that Asian lady beetles are attracted to illuminated surfaces from very long distances. They tend to congregate on the sunnier, southwest sides of buildings illuminated by afternoon sun. Homes or buildings shaded from afternoon sun are less likely to attract beetles. House color or type of siding is less of a factor for attraction than surface contrast.

Contrasting light-dark features tend to attract the beetles — dark shutters on a light background, light shutters on a dark background, windows edged with light-colored trim, gutters and downspouts on contrasting siding, etc. Dwellings near woods or fields are especially prone to infestation, although those in other locations can be infested as well.

Once the beetles alight on buildings, they seek out crevices and protected places to spend the winter. Typical locations include cracks around window and doorframes, behind fascia and siding, and within soffits, attics, and wall voids. Structures in poor repair with many cracks and openings are most vulnerable to infestation.

As temperatures warm in late winter/early spring, the beetles once again become active. This usually occurs first on the sunnier, southwest side of the building. As awakening beetles attempt to escape to the outdoors, some inadvertently wander inward, emerging from behind baseboards, walls, attics, suspended ceilings, etc. Since Asian lady beetles are attracted to light, they are often seen around windows and light fixtures. Lady beetles unable to find their way outside will eventually succumb to a lack of food and die.

IMPACT ON HUMANS. Asian lady beetles cannot breed or reproduce indoors — a fact that should be communicated to customers. Those appearing in late winter/early spring are the same individuals that entered the previous fall.

Besides being a nuisance, the beetles emit an acrid odor and can stain surfaces with their yellowish secretions (see photo, page 84) when disturbed. The secretions contain volatile alkaloid compounds used in defense against birds and other predators.

Although Asian lady beetles do not transmit diseases per se, recent studies suggest that infestations can cause allergies in some individuals, ranging from eye, nose and throat irritation to asthma (see related article, page 88).

People should avoid touching their eyes after handling the beetles, and should consult a physician if they suspect they are having an allergic reaction. When large numbers of beetles are flying in the fall, they often land on clothing and occasionally will bite if in contact with skin. In nature, lady beetles eat other insects and have chewing mouthparts. The bite feels like a pinprick and is seldom serious.

Asian lady beetles are also becoming a concern of the wine industry. Due to their noxious odor, even small numbers of beetles inadvertently processed along with grapes can taint the flavor of wine.

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Allergic Reactions to Asian Lady Beetles on the rise as household exposure increases

By Larry Pinto & Sandra Kraft

We’ve known for some time that many people are allergic to dust mites and cockroaches. In recent years, however, more and more people are also reporting allergic sensitization to lady beetles with symptoms ranging from nasal congestion to asthma. This makes sense since more people are exposed to the beetles every year and allergic responses tend to worsen with increased exposure.

In one survey, 50 percent of respondents reported that their allergy symptoms became worse when lady beetles were in their homes.1 Nineteen percent reported symptoms upon direct contact with the beetle, and 31 percent said they used more allergy medications during fall and spring when lady beetles were active indoors.

Researchers advised physicians to be aware of this potential source of seasonal allergies and should ask patients about possible exposure to high numbers of Asian lady beetles in their homes. In allergy skin prick tests, almost as many patients showed sensitivity to lady beetles as to cats or cockroaches. Sensitization to lady beetles was greater among patients living in rural areas compared to urban areas.

Clearly, it’s a problem that isn’t going to go away and may be getting worse as household exposure to Asian lady beetles increases.

This article was adapted from Techletter, a biweekly publication from Pinto & Associates, Mechanicsville, Md. To subscribe, visit www.techletter.com, or call 301/884-3020.

1Potter, M.F., K. Sharma, H.L. Pence and S.B. Muldoon. 2006. Ladybugs are a new source of allergy. Pest Control. March 2006.

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MANAGEMENT. People’s reactions to lady beetles vary from tolerance to revulsion. The following management tips are provided when the beetles become a serious nuisance within a building:

Vacuuming. The easiest way to remove ladybugs once they are indoors is with a vacuum. Pest managers can provide supplemental vacuuming services, especially in hard-to-reach areas. Brooms also can be used but this may cause staining.

Sealing Entry Points. Sealing cracks and openings is the most permanent way of preventing lady beetles from entering buildings. The best time to do this is in spring or summer, before the adults begin flying to buildings in search of overwintering sites. Cracks should be sealed around windows, doors, soffits, fascia boards, utility pipes, wires, etc., with caulk or other suitable sealant. Don’t buy a cheap caulking gun. Features to look for include a back-off trigger to halt the flow of caulk when desired and a built-in tip cut-off and nail for puncturing the seal of the caulking tube. Silicone or silicone latex caulks that dry clear are easier to use than pigmented ones because they cover mistakes.

Larger holes can be plugged with cement, urethane foam, copper or stainless steel mesh. Repair damaged window screens and install screening behind attic vents, which are common entry points for the beetles. Install tight-fitting door sweeps or thresholds at the base of all exterior entry doors. Gaps under sliding glass doors can be sealed with foam weather stripping.

Light Traps. Asian lady beetles are strongly attracted to ultraviolet light. Consequently, light traps may be useful in capturing beetles in specific problem areas such as attics and false ceilings.

Insecticide Treatment. Insecticides are generally not recommended for elimination of lady beetles indoors. A vacuum is more sanitary and effective. Attempting to kill beetles hibernating in wall voids and other protected locations also is unlikely to be successful and could contribute to secondary problems from scavenging dermestids feeding on accumulations of dead insects. A better approach is to take preventive measures to reduce beetle entry beforehand.

While sealing cracks and openings is a more permanent remedy, comprehensive pest-proofing is sometimes cost-prohibitive or impractical. For structures prone to lady beetle invasion, sealing can be supplemented by autumn exterior insecticide application. Fast-acting residual pyrethroids can be sprayed in a targeted band around windows, doors, eaves, soffits, attic vents, and other likely points of beetle entry. As with other fall invaders (e.g., cluster flies, boxelder bugs and stink bugs), the key is to initiate such treatments before the beetles begin to congregate on and enter buildings to overwinter (late September or October in the Midwest, somewhat later further south). Once the beetles are indoors such treatments would be ineffective.

Unfortunately, there is no simple solution to annual lady beetle invasions. Vacuuming, pest proofing and properly timed exterior insecticide treatments can provide relief but will not prevent entry of every single beetle. Pest managers should take the lead as Asian lady beetle educators and be prepared to offer options tailored to the needs of the client.

The authors are Extension Entomologists at the University of Kentucky, College of Agriculture. The preceding article was adapted from the publication ENTFACT-416. Photos courtesy of M.F. Potter, University of Kentucky.