You may have seen brown marmorated stink bugs in your garden or inside your home and wondered where they came from and why they’ve arrived at your doorstep.
Although these stink bugs aren’t dangerous to people or pets, gardens and crops are a different story.
In this article, we’ll take a closer look at this species and its roots, the destructive appetites of these stink bugs, scientific research into biocontrol methods for combating them, and tactics for keeping them from ruining your garden or invading your home.
- Where do they come from?
- Are they dangerous to humans or pets?
- What do they eat?
- How can they be eradicated?
- How do I recognize a brown marmorated stink bug?
- How do I protect my garden?
- How do I protect my home?
Where do they come from?
Brown marmorated stink bugs (BMSB) are indigenous to Asia, found across China, Japan and Korea.
How they got to America is unclear; one theory is that they may have arrived in the United States on a container ship, and then settled in the mid-Atlantic region. They were first collected in 1996 but only identified as an invasive species in 2001.
They quickly spread across the continent and have now been spotted in most states. By 2010, BMSB were responsible for millions of dollars in losses for farmers and growers, making them one of the worst agricultural pests in the United States.
BMSB are also a severe nuisance pest, invading houses and commercial buildings in large quantities as temperatures drop during the winter.
Are they dangerous to humans or pets?
BMSB do not bite or attack humans or pets. Some people may be slightly allergic to them.
The odor they produce when squashed is unpleasant but harmless.
What do they eat?
BMSB feed on over 100 fruits, vegetables, ornamental plants, and row crops.
They eat by piercing husks or pods with a straw-like appendage and then sucking out juices, leaving no visible trace of their presence.
Stink bugs also feed on leaves, stems, seeds, and trees. Their migration throughout the US is made easy by their varied diet, which provides them with many locations to find food sources.
Enzymes they release during feeding damage organic material, stunting further growth, and leaving pockmarks and pits behind or creating hard blemishes where plant tissue dies.
Produce attacked this way can become pitted or mealy-textured, making it unmarketable as fresh, and potentially even unmarketable as a processed ingredient.
These attacks also open the door for other insect attacks and can spread plant diseases as well.
How can they be eradicated?
No strategy for fully eradicating BMSB has yet been developed. They proved resistant to commonly used pesticides.
Once an effective pesticide was found that could clear a field, frequently the BMSB simply migrated elsewhere, and nothing prevented a new BMSB population from migrating in afterward as the pesticide naturally degraded.
A variety of birds, spiders, and other species eat BMSB, but not in sufficient quantity to halt their spread.
One tactic that scientists studied is biological control or biocontrol.
This is the careful introduction of a natural predator into an affected ecosystem to feed on the pests, thus controlling the pest population without relying on pesticides. No native biocontrol candidates were identified.
In Asia, samurai wasps had been observed as parasitoid toward BMSB, laying their eggs inside stink bug larvae; the larvae are killed when the wasp eggs hatch.
While laboratory studies began to see if samurai wasps could be safely released in America, they emerged on their own in the wild.
These wasps might have arrived here in BMSB larvae as they traveled by container ship or another route to America.
After studying these samurai wasps in the wild, scientists moved forward with rearing and releasing additional wasp populations into affected regions.
The results are promising. Samurai wasps attack 60-90% of available BMSB eggs in a region.
The wasps breed many generations throughout the lifecycle of a single BMSB generation, which lays eggs over the course of several months, so wasp attacks on BMSB eggs remain steady during that window.
And the small, barely noticeable wasps cannot sting humans.
Research on this front is ongoing; it will take time for wasp populations to build up enough to prove out effective for biocontrol.
In the end, eradication isn’t likely, but an equilibrium point could be reached where BMSB populations are reduced enough that the bugs are no longer considered an agricultural pest.
How do I recognize a brown marmorated stink bug?
“Marmorated” means a marbled or streaked appearance. They’re shaped like a shield or an oval and are big enough to spot easily, around the size of a US dime as adults.
BMSB are flying bugs with wings that fold over their backs upon landing; only adults have wings. Their young, called nymphs, aren’t capable of flight as their wings aren’t fully developed until adulthood.
How do I protect my garden?
Many home gardens have been ruined by BMSB in certain regions. Given that releasing samurai wasps isn’t an option for home gardeners, row covers might be a practical deterrent.
A row cover is a lightweight material placed over your garden that protects it during the first frost of a season, but it can also protect against various pests. Large fruit trees can’t be easily covered in this fashion, however.
Because BMSB are big enough to spot easily, you can manually brush them off plants into soapy water to drown them. Look for egg clusters underneath leaves and remove those as well.
You may find it tricky to find locate adults in dense foliage, and simply spraying them with plain water might startle them into dropping off your plants, but they’ll usually return.
How do I protect my home?
BMSB head indoors during the winter and have been known to infest homes and businesses at a scale of thousands of bugs at once.
Their initial goal is hibernation, but warmth in the house frequently triggers activity that can be a big nuisance to residents.
To prevent BMSB from getting into your home, seal it up as effectively as possible.
Look for cracks or openings around locations like window frames, door frames, skylights, electrical outlets, utility pipes, or siding, and use high-quality caulk or sealant to close these routes into the home.
Replace any damaged screens on the windows or doors that you leave open. Install screencaps over chimney tops to keep bugs from entering.
Soapy water traps may kill small numbers of BMSB in rooms of your house. This won’t stop new BMSB from entering, but could at least temporarily clear living space.
Indoor aerosol insecticides rated to kill domestic stink bugs tend to break down quickly and are not a full preventative measure for keeping BMSB out of your home.
Once you’ve realized an infestation is underway, use a vacuum cleaner to remove as many as you can, and discard the bag to prevent spreading the odor of dead stink bugs.
If possible, isolate the BMSB in a single room or location within the house and seal that off to keep the infestation contained. Then call a pest control service to handle clearing them out.
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