I recently get to know this pest that cut off many of my sunflowers. A search in permie forum came back empty so maybe it's not common. Yet I put some photos here in case someone has a similar problem in the future.
My volunteer black oil seed sunflowers mature early and avoided these. They also attack others in the sunflower family, including sunchock, severing the tops. Since adults bugs lay eggs in the dropped flower heads, I make sure to get rid of the flowers on the ground as well.
You know it is dark times when the trees riot. I think this tiny ad is their leader:
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