Central Minnesota Faces Annual Fall Invasion From Asian Lady Beetles And Boxelder Bugs

Asian lady beetles and boxelder bugs have invaded Central Minnesota.  St. Cloud State University Ecology Professor in the Biology Department, Michael Bredeson joined me on WJON to explain why so many Asian lady beetles and boxelder bugs are appearing near homes in the area.

Why Asian Lady Beetles Leave Fields for Homes

Bredeson says it is common in Central Minnesota to see an influx of Asian lady beetles and boxelder bugs in the fall.  He says the reason for this is a couple of factors.  Bredeson says the amount of soy beans growing in the area and mild winters are contributing to the large growth of Asian lady beetles.  He says farmers grow soy beans and aphids flock toward the soy beans with the Asian lady beetles eating the aphids.

Soy Beans Attract Asian Lady Beetles

Bredeson says when farmers combine their soy beans the Asian lady beetles leave fields and head toward higher populations and neighborhoods for a winter home.  Asian lady beetles gravitate toward piles of leaves, hollows in trees and things that will protect them from extreme cold weather in the winter.  Bredeson says attics, between sheet rock, and garages are popular locations.

Why There Are So Many Boxelder Bugs

Bredeson says Boxelder bugs also prefer the same environments that Asian lady beetles like.  He says boxelder bugs are common in neighborhoods with boxelder trees.  Bredeson says this spring saw perfect growing conditions for boxelder trees which set the stage for a large amount of boxelder seeds.  He says the young seeds are what boxelder bugs eat.

Insidious Pirate Bug

A small black triangular looking bug called the Insidious Pirate Bug is another bug found often in the fall in Central Minnesota.   Bredeson says they are small black bugs with a silver patch on their back.  He says they are a native insect that feeds off soybean aphids all summer but like, the Asian lady beetles they leave the fields around harvest time and move toward different locations that can include neighborhoods in the fall.  Bredeson says the small black bug also bites.

How Long do they Stay?

The insects talked about in this story typically stay common in Central Minnesota until high temperatures drop below 45 to 40 degrees.  Bredeson says it wouldn't be surprising to see them exist in high numbers up until Thanksgiving, depending on weather conditions.

If you'd like to listen to my conversation with Michael Bredeson, click below.