Canada thistle

Ghosts in the Mist Thistle

Canada Thistle in southwest Ohio is starting to show the "ghostly" white symptoms of bacterial infections. The tops of infected plants look like they were dipped in bleach. The bacterium produces a chemical called tagetitoxin which is a RNA polymerase III inhibitor that blocks the production of chloroplasts.
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Authors
Joe Boggs

Holey 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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Authors
Joe Boggs

White-Tipped Canada Thistle is not an "Albino Strain."

Canada thistle (Cirsium arvense) plants that are infected with the bacterium Pseudomonas syringae pv. tagetis (PST) develop "bleached tips."  The bacterium produces a chemical called tagetitoxin that is a RNA polymerase III inhibitor that blocks the production of chloroplasts.  Symptoms could be mistaken for exposure to a member of the photosynthesis inhibiting class of herbicide such as the triazines (e.g. atrazine) and nitriles (e.g. bromoxynil).  Of course, the herbicides would tend to affect the entire plant whereas PST only affects the upper portions of...

Published on
Authors
Joe Boggs