Thistle Tortoise Beetle

Canada Thistle (Cirsium arvense) is not Canadian. It’s native to southeastern Europe. Exactly how it got to North America is not known but our friends up north got blamed even though there’s evidence it arrived in the U.S. and Canada at around the same time. Thankfully, Ohioans weren’t involved in the name game; it could have been called “Michigan thistle.”

Damage from the non-native thistle tortoise beetle (Cassida rubiginosa) is beginning to appear on its non-native, invasive host, Canada thistle (Cirsium arvense), in southwest Ohio.  The beetles are pale green or yellowish-green which allows them to blend with their host's leaves.  Like other tortoise beetles, the adults have a body shaped like a flattened pith helmet.  The head and legs of the adults are typically hidden under the flares of their helmet-like body.  The antennae can be hidden or extended out from underneath the front of the beetle.

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