In June I did a post on the problems I was having with my coneflowers The seed heads were turning brown and the flowers were dying. You can read about it here. Taking the heads apart, I found little, tiny worms. After that post, I got several emails from other folks have similar problems. Two of the gardeners were from Ontario, Canada. I want to share one of the emails with you that I thought was really interesting. Her description of the problem matched what I found exactly. This is what she said:
Yesterday I noted my coneflowers were not looking as good as earlier this summer. The leaves look great but the flowers were looking like they were all going to seed. However, I noted no new blooms.So, a closer look identified the heads of the blooms appeared to have dirt on them. Among the dirt, I noted small holes. When I opened a bloom, it contained brown and olive worms. These worms (0.5-3 mm) were eating their way through the blooms. Every bloom with the black dirt contained at least two worms. It seems that 85% of my coneflower blooms have this dirt and worms. So, I have removed all the dirty blooms.Since I have biology training, I know these worms are the larval phase of something. Given the size of the larvae, I can only guess they will mature to be beetles.So, this blog identifies these larvae occur in the Dallas area, in Delaware, and in Ontario. That seems to cover most of central North America.I am going to try to figure out what kind of larvae we are dealing with. One approach is to go in to the compost pile and find a larvae from a coneflower, so I can identify it directly. Or I can find out what other folks here in Ontario are writing about... something that has not turned up on this search tonight.
Interesting, right? I cut off all the infected blooms on mine, and the plants seemed to be ok for the remaining of their bloom time. Perhaps this was a one time problem, but after everyone including the Master Gardeners I talked to said coneflowers rarely have insect or disease problems, I would sure like to know what has developed that is causing problems with people in very different areas. Next year when your coneflowers start to bloom, keep an eye on them and see if you find any problems.