Why so many Asian lady beetles, moths and boxelder bugs?

Some Manitobans are noticing a lot of beetles and moths these days. 

“There are some areas where there are a lot of the Asian lady beetles,” says entomologist John Gavloski with Manitoba Agriculture. “The boxelder bug, it would probably depend on what kind of trees are growing nearby. Areas where there are a lot of maple trees, particularly Manitoba Maple, you’d have more boxelder bugs. 

Gavloski says there are also a lot of green cloverworm moths that migrated into our province earlier this year. 

“Young stage feeds on things like soybeans, beans, alfalfa, clover. They got quite numerous. Now that people are harvesting the soybeans, a lot of the moths are coming off the soybean fields.” 

Gavloski says the population of these insects is not concerning. 

“They can be a nuisance by their presence, for some people,” he says. “They’re not really harmful. Now the Asian lady beetle, it's a newer species in Manitoba, it’s been here since about 2000, they are really good at getting into homes.” 

While these insects are not harmful, they can create quite an odour. 

“Easiest thing to do is just try to physically remove them and put them outside. Don’t squish them, they’ll stink and make a mess,” he cautions. 

This time of year, Asian lady beetles will feed on fruit. 

“Which, if you’re growing grapes to make wine out of, can be a nuisance because if they end up getting crushed with the grapes can taint the wine.” 

As for the boxelder bug, Gavloski says they are no harm to people or pets. 

“They’re just there to overwinter. Once again, just physically remove them. What they feed on as adults is seeds of maple trees. They’ve got no interest in much of what would be in people’s homes.”

Green cloverworm moths. (Photo Credit: John Gavloski)

What about the black moths? 

“The moths I’m talking about, the green cloverworm, they’re going to die out as soon as we get a frost. They won’t get into people’s homes, and they don’t overwinter here. Unless some more migrate in next year, we might not see them again.” 

Gavloski says the best way to keep insects from entering your home is to fill cracks and gaps that could serve as an entrance for them. He says there might be a brief benefit to spraying a deterrent around your home but that would have to be reapplied quite often to have any impact. 

While the Asian lady beetles can be a nuisance in our homes, Gavloski points out that there is a good side to having these bugs around. 

“When we do get them in big numbers, the reason they are in big numbers is likely because we had aphids on our plants and crops earlier in the year.” 

As for boxelder bugs, Gavloski says they are not beneficial in the same way that Asian lady beetles are, but they are also not harmful. He notes the maple trees are not impacted by the beetles feeding on the seeds. 

Boxelder Bugs

The green cloverworm can be considered a pest insect if the numbers are high enough. 

“But it does require very large numbers for them to get to those pest levels. This year, in most cases, they were there, they were doing some feeding, but it wasn’t really a pest issue.” 

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