Coneflowers are sick

Question: For a few years now, I have put up with petaless coneflowers. Now their buds are reduced to 1/4 size and fewer petals. I assume that tiny flea beetles are eating the petals. But what about the stunted inside part.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 28, 2023, 3:04 PM EDT
response: Beetles are a very diverse group but a common culprit for chewing flower petals on emerging buds, and many of them are likely native insects so they are part of the local ecosystem our use of native plants helps to support. Given that, and the fact that any insecticide used to discourage them might harm pollinators visiting the flowers, we do not recommend any sort of pesticide application. You could try knocking the beetles, if you catch them in the act, into a pan of soapy water if you wanted to kill them without resorting to pesticides. Otherwise, the plants won't suffer any long-term damage, even if the reduction in blooms is undesirable. The center of developing flowers might expand normally (that is where the pollinators find their nectar and pollen anyway, not the petals along the edges) but it's too early to tell.  You could trying using a physical barrier instead to keep beetles at bay by gently tying-on tulle bags (like the party-favor fine mesh bags with a drawstring) to the top of the stems until the flower buds are about ready to open; some growers of Dahlias and other cut flowers do this to prevent beetle, earwig, and slug chewing to the buds.  The leaf damage in the third photo (which doesn't appear to be a coneflower -- maybe Agastache? -- though it doesn't matter too much in this case) was caused by Four-lined Plant Bug, a common native insect that has only one generation per year and which has finished feeding. Since this insect overwinters as eggs inserted into plant stems, if they are a persistent and substantial problem, you could try removing plant debris after cutting-back perennials in late winter to see if that reduces the population. Granted, this also removes some habitat for overwintering insects and stem-nesting bees, but when we keep that material in gardens for the benefit of wildlife, we also risk sheltering a few pests, so it's a trade-off because the benefits generally outweigh the detriments.  Miri

responder: The Question Asker Replied July 16, 2023, 12:19 PM EDT
response: Hi Miri’ Thank you so much for this very thoughtful response. My gardening is for “them”-bugs, birds, caterpillars etc. Pollinators don’t much care about perfect flowers. I forgot myself. And never use pesticides either. When I was a little girl, I followed my grandpa as he picked off Japanese beetles from his roses. The beetle problem didn’t last that long anyway. Sent from my iPad On Jun 28, 2023, at 3:04 PM, Ask Extension <<personal data hidden>> wrote:﻿

responder: Answered by theHome and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 16, 2023, 11:52 PM EDT
response: I remember following my father around while he did the same thing. They were wise men and it sounds like you're managing your landscape well.   Christine