I had a learning experience over the past few weeks and I’d like to share what I learned with others! As I was strolling around the garden one evening looking at all the beautiful Black-Eyed Susans in bloom ( Yellow sunflowers above ) I noticed some dead dried leaves that appeared to have been eaten by something. At closer inspection I found 20 or so black “worms” devouring my plants! I was intimately alarmed so I checked out the rest of the plants and sure enough on every Black-Eyed-Sysan plant around the yard and even Coneflowers had 2-3 leaves covered in these worms all munching away. So I ran to the computer to find out what I could apply and get rid of these pests because I was 100% sure they were bad and had to go immediately!
As you can see by the image these “worms” covering the entire stems can look pretty frightening to any gardener. However when I figured out what they were it stopped me in my tracks from doing anything at all. These black “worms” are actually the caterpillars of our native Silvery Checkerspot butterfly! The caterpillars are small and have hairs that give them a pointy appearance, there is also a little orange stripe going down the length their bodies. The adult Silvery Checkerspot Butterfly is a very friendly smaller butterfly and is one of our good pollinators. Something we want to have around our gardens to help pollinate our plants.
Here is what the Silvery Checkerspot butterfly looks like. After seeing this image and going back outside I saw this butterfly hanging around the flowers which helped confirm that these were certainly the caterpillars of this pollinator. Even more interesting like Monarchs, Silvery Checkerspots feed exclusively on a few types of plants in the sunflower family (asteraceae) including Black Eyed Susans and Coneflowers which happen to be two of their favorites.
So after letting the caterpillars stay, this is the damage the caused. You know it’s checkerspot damage because they eat everything but the leaf veins and they feed mostly in groups with several caterpillars on a leaf. Eggs usually hatch in early to middle August, they feed for about two weeks and then they go into hibernation as half-grown caterpillars near the host plants only to finish eating and growing into a butterfly next season. So these butterfly’s don’t leave Iowa in Winter like the Monarch does. As far as the health of the plant goes, yes the caterpillars damage about one quarter of the leaves but this is NOT enough to harm the plant! In fact they will continue to bloom this year and be perfectly fine next year! So if your seeing Silvery Checkerspot caterpillars on your Black Eyed Susans or Coneflowers be sure to let them stay. Because when you plant these types of plants in your yard you are inviting them by creating the habitat they need to continue the next generation. Plus you can’t have butterflys without the caterpillars! So the moral of the story is, look before you spray.