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The Carletonian

The Carletonian

The Carletonian

Asian Lady Beetles: Spawn of Satan or Harmless Knockoffs?

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They look like cute little ladybugs when you see them one at a time. Innocent, spotted, and innocuous. However, as fall sets in, they start showing up in droves, and they swiftly move from cute bug to giant pest. These native lady beetle lookalikes are in fact invasive beetles native to Asia.

These multicolored Asian lady beetle, Harmonia axyridis (Pallas) can be distinguished from their native Minnesotan counterparts by a black “M” on their heads. Besides this easy to identify marking, their coloration varies from all orange, to orange with black spots, to red with black spots.

The lady beetle was first introduced in California in 1916. It was used in California by the Department of Agriculture to combat the pecan aphid, and later, in other states, for other biological control programs. However, it did not become a documented pest until 1988. It is unknown whether the eventual spread of this species was due to intentional introductions or accidental ones that have undoubtedly occurred.

However, in Minnesota it is known that they were never introduced here intentionally, but instead likely migrated in from surrounding states, with their first appearance noticed in 1998.

Their pest status is somewhat nuanced. While people with homes that are invaded by the lady beetle may be adamant on this point, many farmers are thankful for the beetle’s interest in eating soybean aphids. However, the question is even more layered, with the beetles playing negative roles in the growth of other crops and possibly outcompeting native species of lady beetle.

Happily, they pose little threat on a personal level. Though they are known to bite and cause a stench when they release an orange liquid from their joints, they are not known to carry any diseases or cause any structural damage to people’s homes.

In their native habitat, lady beetles winter in crevices on cliff faces. However, in places like Minnesota, they favor houses, especially those with trees nearby and a steady supply of aphids to eat. For this reason, they have be- come a standard fixture of our fall experience.

An unfortunate introduction to our environment on many levels, but a help in some small ways, for now, the multicolored Asian lady beetle is here to stay. And as winter creeps in, they are making their presence known.

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