Coneflower Damage from Sunflower Head-Clipping Weevil
The shiny black weevil feeds about 1 to 1 ½ inches below the flower. They eat a ring of small holes around most of the flower stem. Enough tissue remains so the flower head falls over yet it hangs on a thin bit of tissue. The female enters the flower to feed on the pollen and lay eggs. The flower eventually falls to the ground, eggs hatch and the immature weevil, a worm-like larvae, moves into the ground for winter. Next spring the larvae pupates, then transforms into a weevil and starts feeding on the flower stems in mid-summer.
Remove clipped flower heads from the plant and drop them in a can of soapy water. This kills the adult weevil and reduces the risk of future infestations.
A bit more information: Fortunately this pest is not life threatening, just annoying. Once discovered, monitor plantings to minimize damage and further reduce future infestations.