Purdue News

October 31, 1997

Asian ladybugs wear out their welcome, invade homes

This is a new problem that has caught pest control operators and university entomologists off guard, said Purdue Extension entomologist Timothy Gibb.

According to Gibb, the problem is occurring because a new species of ladybug was imported from Japan to the United States to help control other insect pests. The Asian lady beetle is now found in most of the United States and much of Canada.

"Ladybugs have always been looked upon as beneficial insects worthy of protection," he said. "However, when faced with the emergence of literally thousands of lady beetles inside a home or garage during late winter, the words 'beneficial,' 'conservation' and 'protection' seem to be the last that come to mind."

He suggested that homeowners take these steps now to prevent the ladybugs from getting inside their homes and garages.

• Seal out the beetles by caulking cracks, crevices, and utility service openings; fixing broken window screens and door jams; and plugging cracks in the foundation or roof.
  
• Use pesticides as a perimeter treatment. Gibb recommended using long-lasting residual materials such as wettable powders or micro-encapsulated or suspended-concentrate formulas. "Make these applications by late October or early November. This is key," he said.

The Asian ladybeetle is sometimes called the Halloween beetle because it is orange instead of red, and because it appears on homes and buildings near the end of October. It causes problems because it has an unusual way of surviving winters.

Native ladybugs overwinter individually under bark or in leaf litter. Asian lady beetles, on the other hand, prefer to cluster together in huge numbers on the sides of homes and other buildings. Eventually, as the temperatures drop, they work their way into the building through small cracks or crevices.

According to Gibb, Asian lady beetles are most attracted to:

• Light colored buildings.
  
• Sunlit or southwest-facing sides of buildings.
  
• Buildings located close to trees or woods.
  
• Clusters of other Asian lady beetles that have started forming.

Once inside the building, the beetles are in a hibernation-like state until the first warm days of late winter or early spring when they begin crawling about. "That's the time that most homeowners really notice their company," Gibb said. "A few found here or there might be tolerable, especially in light of their beneficial reputation, but when clusters of several hundred to thousands appear in a living room, bedroom or kitchen, it is hard not to grumble.

"The good news is that when Asian lady beetles occur in the home, they are really only a pest by their presence. They do not feed on or damage anything in the home. They do not bite people or pets, do not infest stored food, and do not destroy household furnishings."

Gibb said that after spending the winter months tucked away in a wall void or other secluded place, the beetles have difficulty finding their way back outside.

"The best suggestion is to help them in their quest by sweeping them up and depositing them outside if possible," he said. "Vacuuming also will work where there are a lot of them. However, be sure to empty the vacuum bag after each time because live beetles can sometimes find their way out of a vacuum left in the closet."

Making the situation worse is that the reawakening may take place over several weeks, depending on temperatures and the size of the population. Continually removing those that become active every day can become a real chore, especially where population numbers are high. "Rest assured that they cannot breed inside the home, no matter what it may look like," Gibb said.

CONTACT: Gibb, (765) 494-4570; e-mail, Tim_Gibb@entm.purdue.edu
Writer: Steve Tally, (765) 494-9809; e-mail, tally@ecn.purdue.edu
Purdue News Service: (765) 494-2096; e-mail, purduenews@purdue.edu

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