This story was originally published in October 2020.
As far as invasive insect species go, the western conifer seed bug is among the more benign. They don’t bite or sting people, nor do they chew on or have a discernible impact on Maine trees. They are, however, related to stink bugs, which makes them a less than desirable house guest.
This is the time of year you are most likely to find them gathering on the outside of your house.
“They are just like the lady bugs that people have problems with,” said James Dill, pest management specialist with the University of Maine Cooperative Extension Service. “This is the time of year you see them clustering on the outside of your house looking for a way inside.”
Like the lady beetles, the western conifer seed bug is looking for a warm place to spend the winter. Now that the days and nights are getting cooler, that search is intensifying and people may be seeing the bug in greater numbers about this time.
The western conifer seed bug is a hard one to miss. The adult is about three-quarters of an inch long. It’s brown with a faint white zig-zag stripe across its midsection. When it flies you can see the bright yellow and orange splotches on its back. It also has two antennae on its head that are almost as long as its body. You can even hear it coming, as it buzzes quite loudly when it flies.
Then there’s the smell.
“They do stink,” Dill said. “If you squish one, it gives off an unpleasant chemical smell and if you disturb it in any way, it will give off that same smell as a defense.”
The seed bugs get into your house through any cracks or openings they can find in the outer walls or around doors and windows. Once inside, they will look for a cozy, dark space to spend the winter months in a dormant state during which they require no food or water. In the spring, once things start to warm up, they will emerge, looking for a way to get back outside.
Western conifer seed bugs have been in Maine for around 15 years and, as the name implies, they feed on the seeds of coniferous trees. They are especially fond of pine trees.
“If you have pines around your house you could be seeing a lot of them,” Dill said. “They really enjoy the pines.”
The insect uses its strong proboscis to bore into the tree seeds and then sucks out the milky juice inside of them.
As bad as that sounds from the trees’ perspective, Dill said the seed bugs are not causing an issue in Maine forests.
“You won’t notice any damage on the trees,” Dill said. “And most of us could care less if there are five or 10 or 100 little pines at the base of a pine tree, and out in the forest they have not made a dent in tree growth.”
If you see any in your house, Dill said the best way to evict them is to use a paper towel to knock them off the wall, pick them up and toss them back outside. If you are feeling less kindly toward the bug, you can dump it into a bucket of soapy water, which kills it.
Reacting with violence is not advised as crushing it releases the pungent odor. Likewise, vacuuming up live western conifer seed bugs will disturb them enough to release their stink.
Spraying the bug with chemicals is not worth the time or effort, Dill said. To be effective you’d have to get up close and hit the bug directly with the insecticide. He said if you are that close, you may as well just knock it into a bucket of soapy water.
To keep them from coming in in the first place, Dill recommends inspecting all around your house and sealing up any cracks or crevices you find.
“They are strong flyers, so be aware of that because when you reach for them they could take off,” Dill said. “Following the screams of people trying to catch them when that happens is a good way to track the bug in your house.”