It won't be long before insects notorious for invading homes in the fall start appearing on our doorsteps in search of winter quarters. The unwelcomed guests may include Boxelder Bugs (Boisea trivittatus); Western Conifer Seed Bugs (Leptoglossus occidentalis); and Magnolia Seed Bugs (Leptoglossus fulvicornis).
Of course, the two most notorious fall marauders are the Multicolored Asian Lady Beetles (Harmonia axyridis) and Brown Marmorated Stink Bugs (Halyomorpha halys). These non-natives have a deserved reputation for invading homes in huge numbers.
However, it's very hard to predict whether or not home invasions across Ohio will be high or low this year, or in any given year. The stink bugs were first found in the U.S. in Allentown, PA, in 1993. By 2010, they had become a major season-long fruit and vegetable pest in the Eastern U.S. Numbers recorded inside homes were apocalyptic for many years. A study published in 2012 reported that over a 181-day study period 26,205 adult bugs were collected inside a single modest-sized home in Maryland.
We braced for the stink bug tsunami to inundate in Ohio; however, it arrived more as a ripple than a wave. I'm not saying there were no Ohio homes with high numbers of stinkers, but home invasions seemed to trend downward rather than upward once the bugs arrived in our state. Still, we can't be complacent. Brown marmorateds were the most common stink bug that I came across this season with numbers on trees and shrubs higher than I've seen in years. Time will tell.
Multicolored Asian lady beetles first became a problem in Ohio in October 1993 when some residents reported that thousands of lady beetles were congregating on homes and buildings, with many of these insects finding their way indoors. Populations remained high in Ohio throughout the 1990s and into the 2000s.
For reasons that remain a mystery, multicolored Asian lady beetle populations began to decline in the mid-2000s with numbers receding to such an extent that the beetles were seldom a problem in and around homes by 2007. However, in 2013, populations began to rebound in Ohio with numerous localized reports of large numbers of beetles entering homes, particularly in the southern part of the state. But the trend has not continued; it remains very much a hit-or-miss proposition.
Some connections have been made between high populations of soybean aphids (Aphis glycines), another Asian invader, and elevated Asian lady beetle invasions in nearby homes. Of course, lady beetles love to chow down on aphids and high numbers of the multicolored Asian lady beetle adults and larvae are common in heavily infested soybean fields. However, using the aphids as a predictor of lady beetle home invasions hasn't been entirely reliable.
What Drives Them Indoors?
Insect fall home invaders do not intend to trespass inside homes and other structures. In fact, those that make their way into the interior spaces of homes are doomed.
As with all insects, the survival of home invaders is governed by a "cold-blooded" physiology meaning the speed of their metabolism is mostly governed by ambient temperature. The higher the temperature, the faster their metabolism, and the faster they "burn" fat. Yes, insects have fat, but it's confined by their hard exoskeletons so they don't suffer embarrassing expanding waistlines.
The home invaders feed voraciously in late summer to accumulate fat. They then seek sheltered locations in the fall where cool temperatures slow their metabolism during the winter so they will not exhaust their stored fat reserves. This survival strategy keeps them alive since there is nothing for them to eat throughout the winter.
The insects are attracted to the solar heat radiating from southern or western facing roofs and outside walls as well as the warmth radiating from within. This can lead them into attics, exterior wall voids, and spaces around door jams and window frames. These all make perfect overwintering sites and they stand a good chance of surviving the winter as long as they remain in these cool, protected locations.
However, they sometimes make a terrible error; for both the insect and a homeowner. Instead of staying put, they continue to follow the heat gradient into homes. This is accidental and disastrous for the insects because the high indoor temperatures cause them to burn through their fat reserves and starve to death. And, they do not go gentle into that good night! Starving stink bugs and lady beetles commonly take flight to buzz-bomb astonished homeowners and terrified pets.
The Best Defense is a Good Offense
The best defense against home invaders buzzing around inside a home is to prevent them from entering in the first place. Although there are effective indoor brown marmorated stink bug traps, they should be viewed as "Plan B." "Plan A" should be closing openings now while outdoor temperatures remain mild and conditions aren't yet driving the invaders indoors.
An ounce of calking is worth a pound of bugs. Large openings created by the loss of old caulking around window frames or door jams provide easy access into homes. Such openings should be sealed using a good quality flexible caulk or insulating foam sealant for large openings.
Poorly attached home siding and rips in window screens also provide an open invitation. The same is true of worn-out exterior door sweeps including doors leading into attached garages; they may as well have an "enter here" sign hanging on them.
Homeowners should also venture into the attic to look for unprotected vents, such as bathroom and kitchen vents, or unscreened attic vents. While in the attic, look for openings around soffits. Both lady beetles and stink bugs commonly crawl upwards when they land on outside walls; gaps created by loose-fitting soffits are gateways into home attics.
Handle with Care
Insects that find their way into a home should be dealt with carefully. Swatting or otherwise smashing these insects can cause more damage than leaving them alone since fluids inside their bodies can leave permanent stains on furniture, carpets, and walls. Also, mashing multicolored Asian lady beetles and brown marmorated stink bugs can release a lingering eau de bug; lady beetles have stinky blood, and stink bugs are called stink bugs for a reason!
As noted above, there are some effective brown marmorated stink bug traps that are baited with a chemical attractant or exploit the bug's attraction to lights. There are even instructions online showing how to construct relatively effective do-it-yourself light traps. The traps can provide some relief with home invasions until entry points are found and closed.
Small numbers of home invaders can be scooped-up and discarded by constructing a simple but effective "bug collector" using a plastic pint water bottle as pictured below. Large numbers of insects can be quickly dispatched by placing a small amount of soapy water in the bottom of the bug collector.
Vacuum cleaners present their own sets of risks. A "direct-fan" type of vacuum cleanershould never be usedunless modified. Passing the refuse through an impeller will create a horrifying bug-blender! However, fragrant misadventures can be minimized with a slight modification involving the use of a nylon ankle sock as shown in the graphic below.
Even a "fan-bypass" type (e.g. shop vacuums) with the refuse bypassing the impeller can develop a distinctive scent if used on stink bugs and lady beetles because the insects will release their defense odor in response to swirling around inside the vacuum tank. Likewise, these vacuum cleaners can be modified as shown below.
OSU Factsheet, Multicolored Asian Lady Beetle