Trick or treaters are not the only Halloween visitors. This is the season when people may notice an invasion of orange and black beetles into their homes.
Sometimes called the “Halloween beetle,” Asian lady beetles are known for beginning their move into shelter at about this time of year.
“If people are seeing lady beetles in their homes right now, it’s almost undoubtedly the Asian lady beetle,” said Doug Landis, a researcher at Michigan State University and with Kellogg Biological Station Long-term Ecological Research (KBS LTER) program.
Around Halloween each year, Asian lady beetles begin their move to shelter, often into people’s homes. Photo: Christie Bahlai
And while homeowners may not be thrilled with these guests, researchers are examining how the beetles control aphids, a pest that eats away at soybeans and other plants.
“We tend to underestimate how much they keep aphids under control,” said Christie Bahlai, a post-doctorate researcher with the KBS LTER program, which has been researching ladybugs for 25 years.
Larger species, such as the Asian lady beetle, can eat up to 100 aphids a day. This saves farmers in the yield of crops as well as the cost of pesticide applications.
Although the lady beetle community is becoming more diverse, exotic species still provide good aphid control, according to Landis. The bugs provide an estimated $240 million value of biological control nationwide.
Arrival of the Asian lady beetles was first noticed in 1993, and by the end of the century the population began to explode, forcing many native ladybugs to retreat from farms and into forests, according to Landis.
Why would one species of lady beetles cause another to move out of its natural habitat?
“They’re just plain better at getting to aphids first,” Bahlai said. “It emphasizes the importance of these forests because they’re harboring native species.”
Soybean aphids first arrived in the Great Lakes region a little over a decade ago. An outbreak occurred in 2001, which coincided with an outbreak of Asian lady beetles. This began a repetitive cycle for the next seven years, with populations rising one year followed by a crash the following year.
Now it seems that lady beetles and aphids are coming to a new equilibrium, Landis said.
Soybeans are generally harvested through mid-September. Aphid outbreaks normally occur until August, and that is often followed by an outbreak of lady beetles.
As cold weather nears and harvesting ends, don’t be surprised to see little orange and black ladybugs in your house reminding you that it is the Halloween season.