I want to thank the gentleman who recognized me at Costco last week and asked how to control the box elder bugs he’d been trying to control this fall. I haven’t dealt with them and welcomed the chance to do some research.
Box elder bugs are native to the Western U.S. and aren’t a serious pest of trees or plants. They are attracted to female box elder tress as well as maple, ash and some fruit trees but usually not in numbers that can damage the trees. They are more of a nuisance in the fall when the adults start seeking out warm places to hide for the winter. Places like cracks in tree bark, crevices in walls and unfortunately, the inside of your cozy house. It’s this penchant to move into a house that makes the bugs persona no gratis.
The bugs are easy to spot given their striking colors of black with reddish orange stripes. They are about a half-inch long and are often found in clusters on house exterior walls or along foundations. They gather on south-facing walls in the fall for warmth before entering a structure through cracks and small holes in foundations and open spaces around windows and doors. Once in the house they often cluster near sunny windows or heat registers.
The good news is that you don’t have to use chemicals to get them out of the house. On outside walls when they are visible, a simple sprayer mixture of a couple of teaspoons on liquid dish soap to a gallon of water applied to the walls will kill them on contact. They have a waxy covering over their exoskeleton that soapy water breaks down, causing the bug to dehydrate. While there are chemicals available to treat them, most experts don’t recommend them because they must be applied every few days and can build up residues on the walls. Additionally, the bugs have become resistant to many of the recommended chemicals.
Inside the house, your vacuum cleaner is the best tool for catching them. When you vacuum them up, remove your bag and either throw it away outside or put it in a plastic bag and leave it in the freezer for a few hours to kill the bugs. Don’t smash them in the house as they will leave a permanent stain on walls and fabrics.
To prevent them from coming inside, repair cracks and holes in walls and foundations and caulk spaces between walls, window sashes, soffit vents and places where pipes and wires enter the house. Repair damaged window screen or add screens.
If they are persistent year after year, look around the neighborhood for box elder, maple or ash trees. If they are on your property, consider removing them. Spraying them, as I said earlier, may not be practical.
Now that the garden season is over and you have time to think, send me questions you’d like answers to over the winter. Email me at pat@inlandnwgardening.com.
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