Coneflowers Have Brown Curling Petals and Red Ants

Normal General Appearance

• Because of its ability to grow virtually anywhere in the United States and also due to its beauty and drought tolerance, the purple coneflower (Echinacea purpurea) is probably the most common species of coneflower in landscapes. It is hardy in U.S. Department of Agriculture hardiness zones 3 through 9. Most types grow from 3 to 4 feet tall, though some petite selections exist that grow to only 1 or 2 feet tall. Shades of magenta and pinkish-purple are the most common, but flowers are now available in almost every color. All coneflowers, beginning in late spring to early summer, wrap up their bloom season by early fall, when the petals and prominent central cones darken to brown. The spent flower heads persist all winter unless cut back, but they are a valuable food source and refuge for birds and overwintering beneficial insects.

Ants on Coneflowers

• In their quest for food and forage for themselves and their nest mates, ants range wide and far and will investigate nooks and crannies on every plant. Seeing ants crawling up and down your coneflowers might make your skin crawl but is generally no cause for alarm. However, a constant, seemingly heavy presence usually indicates the ants are cultivating more troublesome insect pests. Some species, including the red-colored western thatching ant (Formica obscuripes), guard populations of sap-sucking aphids, mealybugs and whiteflies on plants, including coneflowers. The ants farm these insects by protecting them and even carrying eggs underground for overwintering. In turn, the ants get to enjoy a steady diet of the sap-suckers' waste product, the high-energy, sweet honeydew left on the plants.

Potential Damage

• Usually, ants guarding sap-sucking insects colonies on plants pose no problems to either plant or gardener: the ants deter more damaging pests from visiting the coneflowers. However, because sap-suckers feed on the juices of succulent new plant growth, heavy infestations can lead to wilting and slow decline of the plant. More common are fungal infections caused by the honeydew itself, usually manifesting as a topical fungus known as sooty mold. While coneflowers will easily tolerate a light covering of sooty mold, a thick and widespread coating can inhibit photosynthesis and eventually kill the plant.

Sap-Sucking Insect Control

• Sooty molds are best controlled through prevention, meaning control of honeydew-producing insects. Ants are mostly a by-product of this relationship and will seek food elsewhere once their honeydew source is eliminated. Insecticidal soaps are the best and safest choice to treat plants infested with soft-bodied insects like aphids, whiteflies and mealybugs. Apply as a drenching spray to all of the affected plant’s surfaces. Dilute concentrated insecticidal soaps by mixing 2 ½ to 5 tablespoons of soap per gallon of distilled water, and apply once or twice a week in the early morning when there is less chance of it evaporating before it has a chance to work. Do so until pest populations are reduced or eliminated.