Ron Wilson

Ron Wilson

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Fall Invaders are Walking In - Buggy Joe Boggs

This is the time of the year when we typically receive complaints of large numbers of stink bugs, lady beetles, and a few other insects flooding into homes.  However, it’s been more of a trickle rather than a flood this fall, at least thus far.  There have been some exceptions with reports of “hot spots” throughout the states where homeowners feel under siege.


Of course, everything could change with the changing weather.  Typically, fall home invasions occur when an extended period of cool temperatures is followed by a significant fall warm-up.  Thus, the current weather pattern may produce more home invasions. 


The two most notorious fall home invaders are the Multicolored Asian Lady Beetles (MALB) (Harmonia axyridis) and Brown Marmorated Stink Bugs (BMSB) (Halyomorpha halys).  These non-natives have a deserved reputation for invading homes in huge numbers.


Last Thursday, I surveyed members of our OSU Buckeye Environmental Horticulture Team (BEHT) asking what they were seeing with BMSBs in their part of Ohio.  Fifteen responded from around the state, and all reported low to non-existent numbers with only a few reports of the bugs coming into homes.  The striking exception was from Dave Shetlar (OSU Entomology Emeritus, the “Bug Doc”) who is located in central Ohio.  Dave wrote, “My back deck and the double door access have been covered with them for about three weeks.”


BMSBs are primarily viewed as a nuisance pest in urban and suburban Ohio.  However, the bugs can be a serious agricultural pest producing significant injury to ripening fruit and vegetables.  Indeed, large numbers of BMSBs coming into homes in the fall have sometimes been associated with nearby food sources such as orchards and vegetable fields.


Although I have not yet received a report of MALBs crashing domesticated bliss in southwest Ohio, an e-mail message was sent to me yesterday from a homeowner near Darby Creek Park in the central part of the state that included a picture of a large number MALBs crawling on his picture window.  He reported they had arrived en masse yesterday afternoon and some had already found their way into his home.


MALBs make a living like other lady beetles.  Both the adults and the alligator-like larvae chow down on soft-bodied insects such as aphids.  Thus, they are considered beneficial insects.  Indeed, large numbers of MALBs may be found during the growing season feasting on another non-native, the Asian Soybean Aphid (Aphis glycines).


Consequently, homes that are heavily invaded in the fall by MALBs are often located near soybean fields.  Likewise, MALBs commonly target aphids feeding on trees in woodlots and forests making homes near wooded areas focal points for MALB fall invasions.


In the past, Boxelder Bugs (Boisea trivittatus) were well-known for invading homes in numbers that rivaled what we eventually saw with MALB and BMSB.  However, unlike MALB and BMSB, both the adults and nymphs (immatures) of the boxelder bugs would find their way into homes.


Boxelder bugs use their piercing-sucking mouthparts to feed on the seeds of their namesake host, boxelder (Acer negundo), as well as other Acer species and ash (Fraxinus spp.).  Consequently, large numbers of the bugs finding their way into homes were commonly associated with mature boxelders or other maples growing in close proximity to the home.


Boxelder bugs bear a superficial resemblance to our native Bloodsucking Conenose (Triatoma sanguisuga) which may occasionally find its way into homes in numbers of one or two.  The conenose is a type of kissing bug that feeds on the blood of small animals.  The conenose bug does not represent the same threat to public health as those found in Mexico and Central and South America.  However, large numbers of boxelder bugs invading a home may induce panic if mistaken for the conenose.


Other unwelcomed home “guests” may include Western Conifer Seed Bugs (WCSB) (Leptoglossus occidentalis) and Magnolia Seed Bugs (MSB) (Leptoglossus fulvicornis).  These are called “leaffooted” bugs owing to the leaf-like structure on the tibia of their hind legs.


Boxelder bugs, BMSBs, MSBs, and WCSBs belong to the insect order Hemiptera, the “true bugs.”  The name of the order describes the front wings of true bugs with “hemi” meaning half, and “ptera” meaning wing.  The front half of the front wings is hardened and the back half is membranous.


Leaf-footed bugs may be mistaken for stink bugs.  They sequester defense chemicals in thoracic glands and if threatened, they can emit a strong, unpleasant odor.  They also emit a loud buzzing sound when they fly.


Like boxelder bugs, WCSBs and MSBs use their piercing-sucking mouthparts to feed on seeds. This means that homes surrounded by mature cone-bearing conifers may experience fall invasions by adult WCSBs, and magnolias planted near homes may draw in MSBs, both adults and nymphs.


However, I’ve emphasized “may” because home invasions are pretty rare. I’m certainly not suggesting that homeowners should avoid planting trees or worse, cut down trees, as a way to avoid the bugs.  Other less dramatic measures are available to prevent breaking and entering by these and other home invaders.


What Drives Them Indoors?

Insects that invade homes and other structures in the fall do not intend to make their way into heated interior spaces.  In fact, they are doomed if this happens.


Insects are “cold-blooded” (exothermic) 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 within their hard exoskeletons, so they don't suffer embarrassing expanding waistlines.


We are endotherms (warm-blooded) meaning we can generate internal heat to maintain a constant internal temperature.  Of course, an exothermic physiology has some benefits.  Imagine losing weight just by laying out on a sunny beach.


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.


Home-invading insects are attracted to the solar heat radiating from southern or western-facing roofs and outside walls and 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 the insects stand a good chance of surviving the winter as long as they remain in these cool, protected locations.


However, home-invading insects may take their invasion a step too far.  They occasionally continue to follow the heat gradient all the way into the heated spaces.  This is disastrous for the insects and no bargain for the homeowner.


The high indoor temperatures cause the insects to burn through their fat reserves and eventually starve to death.  The homeowners may burn through fat chasing the insects, but they can hit the refrigerator.  The starving stink bugs, lady beetles, and other accidental home invaders do not go gentle into that good night.  They commonly take flight to buzz-bomb astonished homeowners and terrified pets.


The Best Defense is a Good Offense

Homeowners can purchase or construct effective BMSB traps; however, this should be viewed as “Plan B.”  There are no traps for boxelder bugs, MALBs, WCSBs, and MSBs.  "Plan A" should be sealing openings that allow the invaders to invade in the first place.


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 inspect their 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.


Of course, many of these preventative measures to keep home invaders out will also keep heated and air-conditioned air in.  The costs in time and materials can be recovered through reduced home energy bills.


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, smashing the home invaders can release a lingering eau de bug.  Stink bugs are called stink bugs for a reason.  MALBs have stinky blood, and as noted above, leaffooted bugs are armed with cloying, foul-smelling defense chemicals.


There are some effective indoor BMSB traps that exploit the bug's attraction to lights.  There are even instructions online showing how to construct do-it-yourself light traps.  The traps can provide some relief from 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 cleaner should never be used unless modified.  Passing the refuse through an impeller will create a horrifying bug-blender!  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.


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