(and What to Do About Them)
by Brianna Flavin, Ramsey County Master Gardener
9/23/24
Cooling temperatures are the gardener’s signal to start preparing for winter. We might be planting spring bulbs, cleaning our tools for storage or bringing our tender plants indoors.
The shift in weather is also a signal to our insect neighbors to hunker down. And some of them would be happy to do so inside our warm houses.
Read on to see which bugs want to be your roommates—and what you can do about it.
1. Multicolored Asian Lady Beetles
(photo from the University of Minnesota Extension)
Multicolored Asian Lady Beetles look very similar to ladybugs. And contrary to popular belief, they are also big aphid eaters—making them beneficial insects and garden helpers!
But when the weather cools, these useful bugs congregate, looking for warm shelter. The University of Minnesota notes that “they do not infest wood, destroy fabrics, eat food or damage other property, and they cannot sting or carry disease.”
The main issue with these beetles is their tendency to group up, making them a nuisance indoors. One beetle, no problem. Twenty beetles, ew! They can bite if handled, and they can secrete a strong-smelling yellowish liquid which can stain light colored surfaces.
What to do. If you have issues with Asian Lady Beetles in your home, prevention is your best bet. Seal up small cracks in walls (look for areas where electric lines, pipes or vents enter the house) and repair screens and windows.
You can also use a residual insecticide barrier (apply in September or October) to discourage beetles from entering your home. Once they come inside, pesticides are not effective. You’re better off sucking them up with a vacuum attachment. Discard the vacuum bag right away after capturing them, so they don’t escape back into your home.
If you see these beetles inside, just know they tend to wake up when temperatures warm, and they want to get back outside to protect your garden from aphids. They won’t reproduce or multiply indoors.
A little tolerance from you could be beneficial to your plants when spring rolls around.
2. Boxelder Bugs
(photo from the University of Minnesota Extension)
These little black bugs with red banding have specific sites they look for in fall. They love a southern or western facing wall that gets all of that fading autumn sun. If they find a crack in the exterior of your home, they absolutely might wind up inside, taking advantage of the temperate climate.
Much like Asian Lady Beetles, the University of Minnesota Extension points out that these insects are only an annoyance. They can’t cause any harm to humans, don’t carry diseases and don’t cause significant damage to your garden.
What to do. Just like Asian Lady Beetles, an ounce of prevention is worth a pound of cure when it comes to Boxelder bugs. If you’ve had Boxelder bug issues in the past, take time this autumn to look for cracks in your home, especially on west or south-facing walls. Seal these cracks to help keep the bugs out.
If they are already inside, grab the vacuum, suck them up, and discard them outdoors.
3. Brown Marmorated Stink Bugs
(photo from the University of Minnesota Extension)
There are many different types of stink bugs. Some species are native to Minnesota. But the Brown Marmorated Stink Bug pictured here is an invasive species that does some damage to Minnesota fruit and vegetable plants.
As you can see, the adult bugs are brown, with brown and white stripes on their antennae and the ends of their bodies. They look for warmer shelter in the autumn and tend to sneak into older homes or through gaps around old windows. Brown Marmorated Stink Bugs just want to cuddle up and wait until winter is over. During these cold months, they do not lay eggs, reproduce, damage homes, or bite people.
They do sometimes wake up and wander around on warmer days, which is when we tend to see them indoors.
What to do. You don’t need to do anything about these stink bugs unless they bother you. Physical removal, either by hand or vacuum, is the most effective way to get rid of them. It’s best to avoid using pesticides inside your home, according to the University of Minnesota Extension.
Or, just like with the other insects covered here, preventing their entry into your home in the fall will likely cover your bases.
4. Spiders
(cellar spider, photo from the University of Nebraska, Department of Entomology)
While not technically insects (they’re arachnids!), and while also probably in your house year-round, it’s important to mention that a few extra spiders might find their way indoors when winter arrives.
Spiders are not dangerous, do not tend to congregate, and also do not typically lay eggs or reproduce indoors, according to the University of Minnesota Extension. So you don’t have to worry that the presence of a spider is going to cause larger problems. If anything, spiders can be a helpful presence in the home, consuming pests like fruit flies, ants and other bugs that might be interested in sharing your food. Spiders only remain indoors when they’ve found a ready food supply, so I tend to think of them as a mostly-invisible-to-me pest control.
Plus, they make free Halloween decorations! Is that stretching things?
What to do. While you might see some webbing between window panes or the occasional spider skirting your ceiling, the best thing to do with spiders is leave them alone (if you can tolerate their presence).
If not, catching them and relocating them outdoors is the most effective control method according to the University of Minnesota Extension. If your issue is larger than the occasional spider, some pesticides applied to common spider hiding places like gaps, cracks and corners can be effective.
Prevent insects from moving in
As you can see, the common theme with overwintering insect house guests is prevention. Take some time this month to inspect the windows, joints and entries of your home. Pay special attention to any areas near where you’ve seen indoor bugs before. Seal holes and cracks, and if the occasional bug does show up in your house this winter, know that it probably isn’t doing any harm.
Bio: Brianna Flavin is a Ramsey County Master Gardener intern living on St. Paul’s east side with her partner and two young children. She’s especially into berry plants and budget-friendly solutions for making small gardens productive, beautiful and beneficial.