Coneflowers, Echinacea species, add uplifting visual interest to the home gardening space with their erect habit and domed, cone-shaped centers bordered by daisy-like petals in hues of white, purple, pink or yellow. Unfortunately, these showy-blossomed plants come with susceptibility to a variety of problems including pest and disease. Examine your coneflowers regularly to catch problems before they result in permanent damage.
Providing consistent care to your coneflowers promotes vigorous plants that have a greater ability to ward off and recover from problems when compared with plants in poor health. Grow coneflowers in garden areas that offer full sun to partial shade for best growth. These perennial flowering plants thrive in moist, well-drained soil but tolerate periods of drought and warm temperatures. To stabilize soil temperatures, retain moisture and keep weeds at bay, add a layer of mulch to the soil surrounding your coneflowers without pressing it directly against stems. Use a 1- to 2-inch layer of organic mulch like pine bark.
Aster yellows is one of the primary disease problems affecting coneflowers. Aster yellows, also affecting other plants like zinnias and daisies, is a disease caused by phytoplasm, or a bacteria-like organism. This disease occurs on coneflowers when it is transmitted through the saliva of disease-carrying leafhoppers. Aster leafhoppers suck plant sap from coneflower plant tissue, though only a small amount of these pests carry aster yellows disease. Adult leafhoppers are tiny, triangular, winged insects with green bodies and a total length of approximately 0.15 inches.
Japanese beetles also pose a problem on coneflowers. Japanese beetles are chewing pests that display ovular bodies measuring 1/3 to 1/2 inch in length. Beetle bodies exhibit a green hue with a metallic cast and copper wings.
Aster yellows disease is a severe problem that results in the yellowing of leaves, stunted plant growth and blossom distortion and discoloration. Stems often twist and small, misshapen leaves may grow in place of flowers. Symptoms of this disease after leafhopper feeding may not appear for up to 30 days. Before the appearance of aster yellows symptoms, the damage caused by leafhopper feeding results in stippled leaves.
Japanese beetles are "voracious feeders," according to the Clemson University Extension. These pests chew on leaves and flowers, resulting in skeletonized leaves on which only veins remain, loss of blossoms and diminished health.
Look for leafhoppers on your coneflowers during the beginning of spring. Control these pests by applying chemical insecticides like synthetic pyrethroids. Apply up to three times a week. As control is optimal when treating leafhoppers during population spikes, your best option is to contact your local county extension agent for assistance in setting up a control program. If your plant contracts aster yellows, remove and destroy the plant because there are no cures and removal will protect your other garden plants.
For Japanese beetle control, hand pick beetles for smaller problems. For more severe issues, cover your coneflowers with netting or apply an insecticide with the active ingredient cyfluthrin or carbaryl.