Friday, November 1, 2013

Asian Lady Beetle Invaders

From:  Mike Waldvogel and Patty Alder, Extension Entomology 

Just in case the kudzu bugs weren't annoying enough, we have had reports from western NC that the Asian lady beetles have begun their search for winter quarters.  For those of you who are new to this phenomenon, you can read about it at: 

While a lot of North Carolinians spent last week dining on deep-fried everything at the NC State Fair, the beetles have been focusing their attention on crevices in tree bark, rock outcroppings, and (of course) buildings.   The beetles use visual and physical  cues to find suitable overwintering sites. Although these locations  tend to be the sunnier or warmer sides of buildings, or on exposed  light-colored buildings, this doesn't mean that people with dark-colored siding, brick or log homes are immune to the lady beetle assault.  Research has shown that the beetles seem to respond to contrasting and often right-angle shapes or reflective colors, which conveniently (for them) are what windows and doors present against the overall background of a house. Once the beetles arrive at the site, they use chemical cues to locate the specific crevice they want to inhabit within the structure.  The source of these chemical cues may be beetle feces from previous winters (yes... they live and poop inside your walls), or the odor of beetles that died at the site, or possibly an attractant or  pheromone released by the beetles. So, think of your house as the sacred ladybeetle burial ground. 

In some cases, the beetles are a very limited nuisance. However, we have had situations where people's houses have been inundated
with literally thousands of lady beetles.  The sheer numbers of beetles that appear over the course of the winter and spring convince people that the beetles are reproducing in the house. Of course, this isn't true.  The beetles prey mostly on tree-feeding aphids, but they are also found in a variety of agricultural crops.  They lay their eggs on these same plants. So, unless they're growing some "crop" indoors that's infested with aphids (some very mellow and happy aphids) then the beetles are not reproducing or laying eggs in your house.  The  beetles show up because they are simply heeding Nature's call to escape harsh winter weather.

The beetles do not cause real structural damage, if you exclude the odor and yellow-brown stain that they often leave when you disturb or squish them.  There have been reports that the beetles may "bite", but it's more like a pinch (unless you're a real whimp).  There have been published reports of people developing significant allergies from exposure to airborne particulates from decaying lady beetle carcasses. So, the lady beetles aren't entirely innocent of any wrongdoing. 

As with kudzu bugs, pesticides remain questionable in their effectiveness. Some studies have shown that treatments around windows and doors particularly on the south side of the house may have a more significant (but not absolute) impact on the beetle invasions. While frustrated homeowners are anxious to engage in chemical  warfare against the beetles, let's be practical and consider the logistics and safety behind trying to treat sufficient exterior areas of a home to prevent beetles from gaining access.  Even if you do  treat around windows and doors, there is a lot of unchartered territory for the beetles to explore. We still see chemical control as being mostly an exercise in futility.  If people do try to spray pesticides on the exterior of their houses, particularly up high over their heads, please stress to them the need to wear some sort of personal protective equipment, particularly something to protect their eyes, head and other exposed body parts from the chemical mist that rains down upon them and their kids who are watching nearby.  Yes..... keep kids and pets OUT of the area, preferably inside. 

We still recommend the tried-and-true method of vacuuming up wayward beetles indoors, although this recommendation rarely 
appeases irate callers who then make rude, socially unacceptable and physically impossible suggestions as to what you can do with 
vacuum cleaner bags full of beetles. Light traps work well for catching beetles in some situations and this may be particularly important for commercial facilities, such as hospitals and some manufacturing plants, where any type of biocontamination is a critical issue.  These facilities often use the expensive industrial style light traps (not the traditional "bug zapper" type of trap you hang in your yard for summer entertainment).  There is a trap that homeowners can build and use in their homes. These traps will work best at night with minimum interior lighting (i.e., with all lights off) or during the day if you close your curtains to keep out extraneous exterior light and the prying eyes nosey neighbors who want to know what you're doing behind those closed curtains.