The damage to my black-eye susans (rudbeckia species)is worse than ever this year and I’ve even noticed that a big patch of them has not come back. Now it certainly wasn’t because of the cold winter we had–because we had one of the mildest winters ever. So I have to believe that it is because of this pest that’s attacking them.
Despite my best efforts, I’ve not been able to get even another glimpse of the nasty little bug, but some further research, and a conversation with the one of my colleagues from the garden center where I used to work has me now convinced more than ever that this is indeed an insect and not a fungus. I just do not know why more folks haven’t caught onto this.
This post from the University of Connecticut IPM program, describing the four-lined plant bug and the damage it causes, has not only nailed down the problem exactly, but it has made me wonder if I haven’t misidentified the pest somehow and if I don’t have four-lined plant bugs on the black-eyed susans. It scarcely matters–the result is the same–I have a hard-shelled beetle type creature that I can’t see doing so much damage to my plant that I can’t believe it.
Further, my organic controls are not really going to work all that well (thankfully, these guys only have one generation a year where I live!) But I’m going to have to find something to stop them because I don’t find the egg masses to wipe them out early!
Here’s what UConn has to say about this bug: Feeding causes brown spots on the young foliage. Because the spots are round and fairly uniform, many gardeners mistake it for a disease. The insects are fast-moving and rarely seen, so most gardeners are further convinced they have a disease, not an insect on the plant. Finally, the injured tissue may fall off the plant, further giving rise to disease like symptoms. This is why garden centers for years have been selling gardeners fungicides to “treat” this problem.
And because the insects have one life cycle, there may even be the illusion that the fungicides work (which a true fungicide rarely does, by the way. It can control disease, but not cure it. FYI).
So the next time your black eyed susans look this bad, run for the insect ID book, not the fungicide. Meanwhile, I’ll try to find those nasty overwintering eggs this autumn since chemical controls are not an option for me.