We have seen similar beetles before but have not yet managed to ID them to species level. They resemble Brachypnoea tristis (which has no common name), or perhaps others in that genus. We have encountered them on both Rudbeckia (Black-eyed Susans) and Echinacea (Coneflowers).

They don't cause serious damage to long-term plant health, but use of an insecticide if they are decimating flowers or buds is not practical or recommended when the plants are grown for pollinators or other wildlife use. (The active ingredient spinosad, for example, can be toxic to bees, even though it targets leaf-chewing insects.) Nor would the other solution to excluding leaf-chewing pests, insect mesh netting like that used over vegetables, be useful since it would block access to the blooms for pollinators.

While lower-toxicity sprays like horticultural oil (neem and others) and insecticidal soap can help to manage some pest insects, adult beetles are not as vulnerable, and sprays would need to directly coat them to be effective. Therefore, it would be more practical (since the pests need to be present for both methods) to just knock them into a pan of soapy water to kill them if intervention is necessary. Birds, spiders, and other predators will probably pick off some of them over time. Given the long bloom period of these plants and the more limited adult activity period of these beetles, once the beetles have disappeared, the plant should still bloom.

Miri

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