During the warm, sunny days of spring, some insects may become a nuisance as they leave their overwintering locations and seek the warm rays of spring sunshine. Our master gardener volunteers tend to get calls this time of year seeking information on controlling such insects as ants, stink bugs, lady bugs and boxelder bugs.
Dealing with insects is never tops on anyone’s list, but having portions of your home’s foundation covered with small black and red insects may make you feel like you are in an old-time horror movie! Of concern lately for many homeowners and even businesses are boxelder bugs. The boxelder bug (Boisea trivittata) is a true bug (not a beetle) and is a native species to North America. It is found primarily on boxelder trees, but can also be found on maple and ash trees.
The boxelder tree (acer negundo) is a fast-growing maple tree species native to North America and is also known as ashleaf maple, Manitoba maple, boxelder maple and western boxelder. Although drought-resistant, boxelder trees do not have a lot of ornamental appeal to homeowners. They reach a height 50 to 75 feet, with a trunk diameter up to 4 feet. The trunk is relatively short and tapering, and the crown is spreading and bushy. There are male boxelder trees and female boxelder trees, and we will see why this is important shortly.
Boxelder bugs are a pest of outdoor trees as well as a household nuisance, and have been creating a lot of conversation this winter. This is an interesting insect. It overwinters as an adult in the bark of trees, but will also choose buildings and houses to spend the winter. In fact, this year, our office has seen a number of these unwanted guests in the building for the first time! Their appearance has generated some lively lunchroom discussions. The good news is they do not feed while indoors, nor do they bite you or your pets.
Wondering what the boxelder bug looks like? It is about half an inch long, is dark brown to black in color, and has red stripes on the body and wing margins. During warm, sunny winter days, they can be seen in large masses warming up on the side of buildings. That's no cause for alarm, as they do not feed on anything either inside or outside of your house. They are just a nuisance.
Now that the weather is starting to warm up, they are leaving their place of hibernation and fly to boxelder trees, where they deposit their eggs in the cracks and crevices of the tree’s bark. The eggs hatch in 11 to 14 days and are called nymphs. The nymphs are bright red and look like the adults, but cannot fly or reproduce. The change from nymph to adult is gradual.
The nymphs will feed on the seeds of other maple trees and plants, as well as boxelder seeds. They tend to cluster around female boxelder trees. Female boxelder trees are identified by the seed pod they produce, which looks similar to other maple tree seeds.
To manage these insects can be challenging. Since the presence of these bugs is associated with boxelder trees, removing the tree and replacing with another tree species can be one option, or you can consider keeping only the male boxelder tree. However, it is reported that these insects can fly up to 2 miles, so alternatives to removal might need to be explored.
Other options to control the boxelder bug have included washing the insects from the sides of buildings with a garden hose or pressure washer, only to have them return. If they are overwintering in firewood, covering the firewood pile may discourage them. Pesticide applications outdoors on buildings can be made by a certified applicator using a target perimeter treatment.