Agriculture - Multicolored Asian Lady Beetle

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Independence County
Agriculture
Household Pests - Multicolored Asian Lady Beetle

Lady beetles, which are sometimes called ladybugs or lady birds beetles, are familiar insects in may parts of the United States. For the most part, lady beetles are beneficial predators that consume aphids, scale, insects, and many other pests that injure plants in gardens, landscapes and agricultural settings; however, in many places the multicolored Asian lady beetle (Harmonia axyridis) has become a household pest over recent years. In Asia, this beetle feeds on aphids and other soft-bodied insects that dwell in trees. Cracks and caves in cliff faces provide perfect locations for large aggregations of these lady beetles to hibernate (overwinter). Unfortunately, in the United States where cliffs are not prevalent these insects seek overwintering sites in and around buildings.

Picture of lady bugs with a nickel comparing size to nickel.

Thus, during the last decade, the multicolored Asian lady beetle has become an unwanted household guest, especially during the spring and fall months. The multicolored Asian lady beetle was first recorded as a pest in houses in 1988 in Abita Springs, Louisiana. It had been first released in the early 1900s as a biological control agent; and numerous subsequent releases have been made throughout the United States. Because the beetle was not recovered after these release, it was assumed that it had not established and was incompatible with North American conditions. The source of the 1988 infestation in Abita Springs, LA is unknown; but it is not thought to be linked to the controlled releases.

The original infestation site was close to ports used for international shipping including cargo containers from Asia. Since this inadvertent release, the beetle has rapidly expanded its range and is now commonly found throughout much of the U.S. Large congregations tend to be found on windows, doors, and porch decks, and in the walls of buildings.

Picture of thousands of lady bugs.

Description

Multicolored Asian lady beetles are slightly larger than most native lady beetles, with adults measuring 9/32 inch (7mm) long and 7/32 (5.5mm) wide. They are oval or convex in shape, and yellow to red in color (without black spots on wing covers). The beetles' spots, which can vary in size and pattern, number from no spots to as many as nineteen; however, nineteen is the most common number. The head is usually concealed beneath the disk-shaped pronotum, which is cream to yellow in color with a black 'M' design in the center. Asian lady beetle larvae are elongated, flattened, and covered with minute tubercles or spines. They are often described as alligator-shaped. The eggs, which are laid upright in clusters of about twenty, are oval and yellow.

Life Cycle

Large lady beetle populations typically build up during cool, wet summers that favor healthy plant foliage and large aphid infestations. The life cycle from egg to adult requires about a month, depending on the weather. Eggs hatch in 3 to 5 days. Larvae feed for 12 to 14 days. During which time they consume large numbers of aphids, scale insects, and other soft-bodied insects. Pupation lasts 5 to 6 days until adults emerge. The adult stage is the longest with some lady beetles living up to 2 or 3 years.

Eggs	Larva
Pupa	Adult

Once the weather starts to turn colder, lady beetle adults begin to seek overwintering sites. The lady beetles appear to orient toward light colored, conspicuous objects, such as white buildings. Large numbers collect on outside walls warmed by the sun, especially on the south and southwest sides. When one lady beetle lands, many others soon follow. Some research suggests that this aggregation behavior may involve chemical cues (pheromones), visual cues, or a combination thereof. However, additional research is needed.

Benefits

The multicolored Asian lady beetle is a voracious predator of aphids and scale on trees, shrubs, and crops. Adults are capable of consuming 90 to 270 aphids per day and larvae can consume between 600 and 1,200 aphids during its life stage. Both adults and larvae have been observed in soybean fields feeding on the newly introduced soybean aphid and are believed to be effective biological control agents in controlling this important new pest.

Damage

The greatest damage caused by the multicolored Asian lady beetle is the discomfort they give to homeowners. It is not uncommon for tens of thousands of beetles to congregate in attics, ceilings and wall voids. When the heating is turned on the beetles tend to move around inside these voids and exit into the living areas of the home.

In addition to beetles biting, they exude a foul-smelling, yellow defensive chemical, which will sometimes cause spotting on walls and other surfaces. Most people are only annoyed by the odor of these chemicals. However, some individuals experience an allergic reaction to the defensive excretions. Rhinoconjunctivitis (sinus irritations) and mild skin irritations have been reported subsequent to encounters with the multicolored Asian lady beetle. It is probably not an over-reaction to wash hands or other skin after contacting the beetles. In at least one study, the severity of rhinoconjunctivitis subsided with the removal of beetles from the home.

Management Approaches

The best management recommendation is to prevent multicolored Asian lady beetles from entering the home or building. Preventive measures should include a variety of non-chemical pest-proofing tactics. Take measures to exclude these lady beetles before late autumn when they begin to seek overwintering sites in structures. This can be done by sealing all outside cracks and crevices around doors, windows, siding, utility pipes and other openings with a good quality silicone or silicone-latex caulk. Window screens should not have any tears and should fit snugly inside the window frame. Install insect screening over attic and exhaust vents.

If numerous lady beetles are entering the living areas of the home it is advisable to locate the places where the beetles gain access. Typically, beetles will emerge from cracks under or behind baseboards, around window and door trim, and around exhaust fans or lights in ceilings. Seal these openings with caulk or other suitable materials to prevent the beetles from crawling out. A temporary solution is to use tape to stop the beetles. A helpful hint to remember: the beetles are attracted to light and can see light entering through cracks in the walls or ceilings. Initially, concentrate on sealing cracks in the rooms where beetles are most prevalent.

Black (ultra-violet) light traps may provide relief from beetles flying or crawling around the interior of homes. These traps are available for purchase from pest control companies and pest control supply companies. A description of a trap is available from the USDA at http://www.ars.usda.gov/is/br/lbeetle/001030.trap.pdf describing the items necessary to build your own. If you decide to buy a trap, get one that has a sticky glueboard trap to collect the beetles. The glueboards can be replaced when they become full of beetles, although this might only be practical to remove small numbers of lady beetles. DO NOT use the type of light trap that utilizes an electrical grid (commonly called 'bug zappers') to kill the beetles inside the home. Light traps are most effective at night when there are no competing light sources, or during the day when curtains are drawn and other light sources are minimized.

The use of a vacuum is still the most efficient method of collecting beetles in the home. The major complaint for this method is that the beetles become agitated and expel the yellow, foul-smelling repellent, which is then circulated into the air by the vacuum exhaust. Also, it is advisable to empty the bag and beetles after each vacuuming to prevent them from escaping back into the house. It is possible to capture the beetles inside a knee-high nylon stocking that has been inserted into the extension hose or wand and secured in place with a rubber band. As soon as the vacuum cleaner is turned off, be sure to remove the stocking so that the captured beetles cannot escape. As you remove it, the rubber band closes around the stocking, effectively "bagging" the lady beetles. You then can discard the contents of the stocking. This way you will not need to change the bag in you vacuum every time.

If you have encountered large, persistent infestations of lady beetles, pesticides may be used in addition to other control efforts.

This information was abstracted from the Ohio State University and Pennsylvania State University and the Pest Management Center Multicolored Asian Lady Beetle fact sheets.

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Independence County Agriculture Household Pests - Multicolored Asian Lady Beetle

Independence County
Agriculture
Household Pests - Multicolored Asian Lady Beetle