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When good ladybugs go bad

Trade shows keep our marketing department busy in September and October. (Which explains the light posting recently.) This year's shows had us pitching our insect traps to retailers in Las Vegas, Reno, Napa, Baltimore and Philadelphia.

It was at a fall trade show several years ago that some True Value dealers started asking me about a small orange beetle that showed up in their homes in large numbers during the fall months. We sell a Japanese Beetle Trap, and the dealers thought that perhaps that product would solve their problems with this home-invading insect of Asian origin. Desperation was evident on their faces as they described the noxious odor and yellowish fluid the beetles emitted. Most reported trying to vacuum up the beetles from the walls and ceilings where they congregated, but this tactic seemed to only make the problem worse.

Turns out that this insect pest is actually a ladybug... a sweet, innocent ladybug -- the most recognizable of all the beneficial insects. How did the good ladybug go bad and become a pest?

Asian_ladybug_usda_photo_1 Actually, this bug is still technically a good bug, even though it's a nuisance to people when indoors. This particular species of ladybug is named Harmonia axyridis -- or, more commonly, the Asian lady beetle. Like others of its kind (ladybugs, that is), H. axyridis is valuable to gardeners and farmers because it eats aphids by the hundreds. It also devours other soft bodied insects that are pests of ornamental plants, vegetables and fruit trees.

As for appearance, the United States Department of Agriculture says that compared to other lady beetles, "H. axyridis has a wider range of colors and spot numbers... Wings range from black to mustard; spots number zero to many. The most common United States form is mustard to red with 16 or more black spots. But the species is easy to identify from its big false 'eyes' -- twin white football-shaped markings behind the head."

The USDA reports that when the Asian lady beetle first came on the scene, it was accidental. The bug was originally a stowaway that first became established from ancestors that entered by ships coming from Asia to the ports of New Orleans and Seattle. In the 1970s and 1980s, USDA entomologists released large numbers of Asian lady beetles in the South, East and Northwest to research their effect on crops -- one of which was pecans. According to one of the scientists involved in the study, the beetle "nearly eliminated pecan aphids" where it was present.

Okay, so it eats aphids and other insect pests, and that's all good. But its presence near homes has been a mixed blessing. According to a researcher at Colorado State University, the Asian lady beetle has now acquired a bad reputation stemming from its autumn habit of invading houses and buildings in search of overwintering sites.

Ladybeetlemass The theory is that the beetles favor light-colored buildings and sunny, south-facing walls. They look for cracks and crevices where they can sneak in and hibernate en masse.

The CSU article continues: "Their ability to reflex bleed, leaving stains on walls, curtains, etc., distinctive odor, and habit of becoming active on warm days has led to their additional designation as an insect pest."

I definitely can't blame the people who have labeled these ladybugs as pests. Beetle juice, beetle stains, and beetle stink in my house would not give me any warm and fuzzy feelings towards them. Some individuals have even reported that they bite people.

Personally, I'd have to look at Asian lady beetles the way I look at bats. Yes, I understand they are beneficial because they eat bad bugs. And they don't mean any harm to people. But if they invade my house, they are a nuisance and I want them dead.

According to news stories found here and here in recent days, people in West Virginia may be dealing with Asian lady beetles even as I blog.

October 26, 2006 in Asian lady beetles | Permalink


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Posted by: Tom Clarke | Sep 13, 2007 11:04:59 PM

While it mentions how good they are at devouring Aphids etc. it does,t mention if it has it's own preditors which I think may be a big part of the problem

Posted by: Brian Page | Apr 21, 2008 5:09:48 PM

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