Summer has a way of delivering a steady stream of head-scratchers in the home landscape, its own good, bad, and ugly playing out among the leaves. Every season brings a new cast of characters riding into the garden: leaves that look wrong, flowers that no longer look like flowers, and a rotating lineup of insects that range from alarming to downright fascinating. But before you reach for the spray bottle and run them all out of town, here's a look at five making the rounds right now. Some are worth watching, some are just passing through, and a few are the best allies you've got."
American Beautyberry, Callicarpa americana: Cucumber Mosaic Virus
If the leaves on your American beautyberry (Callicarpa americana) look mottled, blotchy, and a little puckered, there's a good chance you're looking at Cucumber Mosaic Virus, or CMV. It's one of the most common viral diseases in the home landscape and it has a very characteristic look: yellow-green mottling that tends to follow the leaf veins, with some mild leaf distortion alongside it.
Don't confuse it with herbicide drift, which typically shows up as uniform strapping or cupping of new growth, or with nutrient deficiency, which tends to cause more even interveinal yellowing rather than patchy, irregular mottling. CMV is spread by aphids moving from plant to plant, and once a plant is infected there is no cure. The plant will often continue to flower and fruit normally, so removal isn't always necessary. Keep up with aphid pressure on surrounding plants, remove severely affected material, and don't compost it.
If your purple coneflower (Echinacea purpurea) bloomed this year and the flowers came out green, malformed, and barely recognizable, that's almost certainly aster yellows. It's caused by a phytoplasma, a bacteria-like organism spread by leafhoppers, and on coneflowers it produces one of the most striking and unmistakable symptoms in the landscape: spoon-shaped greenish petals, distorted cone centers, and an overall stunted look that leaves you wondering if something went seriously wrong.
Something worth knowing: coneflower rosette mites can produce similarly distorted flowers and are sometimes confused with aster yellows. With aster yellows, the whole plant tends to be affected and the coloring stays consistently green and abnormal rather than just the flower center. Like CMV, there is no cure. Remove and destroy affected plants, don't compost them, and keep in mind that leafhoppers are highly mobile and pick up the phytoplasma from infected weeds throughout the landscape. Controlling the vector is difficult, so sanitation is your best tool.
For the past several weeks you may have noticed a rather large and ominous insect buzzing about your home landscape. What you've probably encountered is the cicada killer wasp, and despite its appearance, this is not one of those times to be alarmed. Cicada killers are referred to as gentle giants for good reason. They approach 1.5 inches in length, about the size of your thumb, with bands of white and yellow stripes on a black body and wings tinged yellow.
A telltale sign of their presence is the mound-like structures they leave in the ground, often mistaken for fire ant mounds. These are solitary wasps, meaning each female has her own burrow. They prefer sandy, well-drained sites and show up on playgrounds, golf courses, and garden beds alike. The males are the ones you see flying about frantically and hovering near the mounds. They're extremely territorial and will square off with other males to attract a female, but they cannot sting. Females can sting but won't unless you accidentally step on one or disturb her burrow directly. As the name implies, cicada killers prey on cicadas, paralyzing them in flight and dragging them back to the burrow as food for their larvae. In a typical season, 100 female cicada killers will remove over 16,000 cicadas from the surrounding area. Control is rarely warranted. If mounds are in a high-traffic area, reroute foot traffic around them and let them do their work.
The potter wasp might be the most fascinating beneficial insect in the summer landscape that almost nobody knows by name. The fraternal potter wasp (Eumenes fraternus) is a small, shiny black wasp less than an inch long, with white markings and a distinctive elongated abdomen. What sets it apart is its nest: a tiny, perfectly formed clay pot, about half an inch across, often found on the underside of a leaf. The female collects water and soil, mixes it with her own saliva as a natural adhesive, and fashions the urn over the course of an hour or two. She lays a single egg inside, stocks it with about a dozen paralyzed caterpillars, then seals it shut. When the egg hatches, the larva has everything it needs.
Potter wasps are solitary and docile. They are nectar feeders as adults and pose virtually no threat to people. They also provide outstanding caterpillar control, which makes them valuable allies in the garden. If you want to encourage them, plant some of their favorite nectar sources: fleabane (Erigeron), mountain mint (Pycnanthemum), goldenrod (Solidago), and boneset (Eupatorium) are all excellent choices and support a wide range of other beneficial insects as well. If you spot a small clay pot tucked under a leaf somewhere in the garden this summer, leave it alone and count yourself lucky.
If you grow milkweed and have noticed caterpillars working through the foliage, take a closer look before you do anything. The milkweed tussock moth, also called the milkweed tiger moth, is a native insect and a legitimate part of the milkweed ecosystem. Young larvae are bright yellow and black, and older caterpillars develop a striking mix of black, white, and orange tufts that make them genuinely hard to miss. They feed in groups early on and can defoliate sections of the plant quickly, which tends to alarm gardeners.
Here's the thing: milkweed is tough, and defoliation from tussock moth caterpillars rarely causes lasting harm to an established planting. These are native insects that belong on native milkweed, and they share that resource with monarchs throughout the season. If your milkweed is heavily loaded, you can move caterpillars to a less impacted plant. Otherwise, let them do what they do. The adult moth, a modest gray-and-yellow creature, is perfectly harmless and every bit as native as the milkweed it calls home.
When in Doubt
If you've got something in the garden that doesn't match any of the above, the NC Plant Disease and Insect Clinic at NC State University accepts samples from homeowners through your local Extension office. Bring a sample by the Nash County Center and we can help get it submitted.
Extension Resources
This article draws on Extension resources from NC State and neighboring land-grant universities, including NC State Extension, the NC State Extension Plant Toolbox, and Clemson Cooperative Extension's Home & Garden Information Center.
