False Lady Bugs: History, Life Cycle, Environmental Impact, and Control Strategies
The multicolored Asian lady beetle (Harmonia axyridis), often mistaken for native ladybug species, has become both a beneficial insect and a household nuisance in the United States. Understanding its history, life cycle, environmental impact, and effective control strategies is essential for homeowners and pest control professionals alike.
History in the United States
Native to eastern Asia, the multicolored Asian lady beetle was introduced into the U.S. multiple times throughout the 20th century, primarily to control agricultural pests like aphids and scale insects. The first established populations were observed in Louisiana in 1988, and by the early 1990s, the beetle had spread to multiple states, including Pennsylvania. In Pennsylvania, adult beetles were first observed during the fall of 1993, congregating in large numbers on windows, doors, and porch decks. (Penn State Extension)
Life Cycle
The multicolored Asian lady beetle undergoes complete metamorphosis, consisting of four stages: egg, larva, pupa, and adult. Females lay clusters of yellowish eggs on the underside of leaves near aphid colonies. These eggs hatch into larvae that are elongated and spiny, progressing through four instars (molts) over approximately two weeks. After the larval stage, they pupate, and adults emerge in about five days. The entire development from egg to adult typically spans 15 to 25 days, depending on environmental conditions. (Northeast IPM)
Environmental Impact
While introduced as a biological control agent, the multicolored Asian lady beetle has had unintended consequences on native ecosystems. Its aggressive nature and high reproductive rate have led to competition with native lady beetle species, resulting in declines in native populations. Additionally, these beetles can become pests themselves, especially when they seek shelter in homes during the fall to overwinter. They can emit a foul odor, leave stains on surfaces, and may even bite when disturbed. (Penn State Extension, Pennsylvania Department of Conservation and Natural Resources)
Strategies for Dealing with Infestations
Managing infestations of multicolored Asian lady beetles requires a combination of preventive measures and control strategies:
- Seal Entry Points: Inspect homes for cracks, gaps, and openings, especially around windows, doors, and utility openings. Use caulk or weather stripping to seal these entry points, preventing beetles from entering. (Northeast IPM)
- Use Physical Barriers: Install screens on windows and vents to reduce the likelihood of beetles entering the home. Ensure that existing screens are in good repair without holes or tears.
- Vacuuming: If beetles do enter the home, use a vacuum cleaner to remove them. This method is effective and prevents the release of their defensive odor and potential staining. Dispose of the vacuum bag promptly to prevent escape. (Northeast IPM)
- Exterior Treatments: In cases of severe infestations, consider applying insecticides to the exterior of the home, focusing on areas where beetles congregate. It’s advisable to consult with pest control professionals to select appropriate and effective products. (Pennsylvania Department of Conservation and Natural Resources)
- Indoor Traps: Light traps designed for indoor use can attract and capture beetles that have entered the home, reducing their numbers without the use of chemicals.
By implementing these strategies, homeowners can effectively manage and reduce infestations of multicolored Asian lady beetles, balancing the benefits they provide in pest control with the nuisances they can cause in domestic settings.
References
Featured image credit: https://www.insectimages.org/browse/detail.cfm?imgnum=5410811
