Asian ladybird beetle (Harmonia axyridis)
With Dr. Carcamo, John Acorn & Brendan Roy
Farming Smarter recently hired a keen entomologist as a research technician, Brendan Roy, He is always alert to what might be crawling in the snow, say for example a multicolored ladybird beetle. Especially, when that ladybird beetle is a potential invasive pest. Yes, a ladybird that is a potential pest, that is what Brendan retrieved from the snow while working in the research plots near Lethbridge. The Asian ladybird beetle (Harmonia axyridis) also known as the harlequin ladybird, is one of those insects with a good and a bad side.
The Asian ladybird came to North America to help native ladybird beetles control aphid pests. So this is its good side: it is a voracious predator of aphids. For example it eats many soybean aphids and helps farmers growing soybean and other crops aphids attack. In Alberta it used to be released in greenhouses to reduce aphids and other insect pests.
Unfortunately its bad side probably outweighs its good side. When aphids become scarce it will eat other ladybird beetles to the point that it will negatively affect populations of native species. This has resulted in a marked decline of native species in the many areas it is well established. It has also been observed to eat grapes when it runs out of insect meat.
In those well established areas, such as south eastern Manitoba, in preparation to overwinter it can form large aggregations in buildings where it becomes a nuisance. Adults release a foul yellow liquid when they are handled and yes, they have the bad habit of nipping people too.
John Acorn from the University of Alberta who calls them Halloween Ladybugs, southern Alberta has scattered reports of individuals caught in late fall as the one caught by Brendan in the snow. His thoughts are, “my personal prediction is that this species will not become more common in Alberta, since it seems to do best in places that are a lot more moist (think west coast, or the eastern deciduous forests). That’s my bold prediction!”
Albertans should still watch for these ladybugs and report them because, although it happens rarely, he could be wrong!
For a detailed account on their biology, ecosystem impacts and bibliography see: Animal Diversity Web
Created November 18, 2020 | Category: Bug of the Month