I am revisiting this topic for two reasons: first, because it is one of my most searched posts this time of year, but also because I’ve recently found a great chart from the University of Illinois that lists 20 different insects that feed on various parts of black-eyed susans (Rudbeckia species). Granted, we most likely won’t all have all of those insects in our garden, but I do surely recognise a good number of them including the four-lined plant bug, the little nasty critter I keep insisting is responsible for the leaf damage to mine (the black spots).
You can access that chart here. One of the interesting things to note is that quite a few of the early insects listed are butterflies or moths. This means that the black-eyed susan is serving as the nectar plant for them–a very nice thing.
As you read further down the chart, any insect listed with an asterisk (*) next to its name feeds on the petals. That means it most likely is the nymphal stage of the butterfly, so it’s going to be a caterpillar. I know I for one don’t want to be in the habit of squashing caterpillars randomly, particularly ones that belong to butterflies. I’d rather endure petal damage.
Finally as you look down the chart you see my “baddie” the four-lined plant bug and some other true bugs. Now you have some hard choices to make. Knowing that you’ve got butterflies and their larva feeding on these plants, what do you do?
As you can tell by any damage in my garden, I tolerate the damage for the sake of nature.
Intereestingly, notice that one of the petals in the centermost flower has a notch taken out of it. I didn’t notice the damage until I uploaded the photo. Those semi-circular notches are made by leaf-cutting insects–bees or ants most likely. They do not harm the plant (other than by taking the piece of the petal or leaf away and visually disfiguring it). They use the piece taken away for nesting.