10 Common Coneflower Pests and Diseases to Watch For

Despite their hardiness, all types of coneflowers (Echinacea spp.) can suffer from diseases and pests. In my experience, common coneflower diseases include aster yellows, leaf spot, powdery mildew, and stem or root rot. Pests include aphids, Japanese beetles, and whiteflies. I find the best solutions to treat these issues include insecticides and neem oil. In this essential guide, I’ll cover ten common coneflower pests and diseases and how to identify and deal with them.

10 Common Coneflower Pests and Diseases

How to Identify Common Coneflower Pests and Diseases

Although coneflowers are incredibly hardy, diseases and pests can still cause problems. Diseases may infect coneflowers due to poor growing conditions or contamination from unsterilized cutting tools. Pests can be attracted to coneflowers not growing in ideal conditions as these plants are weaker and more susceptible.

Here’s a rundown of 10 common coneflower pests and diseases and the symptoms you can use to identify them:

1) Aster Yellows

Aster Yellows impacting a single pink coneflower plant

Aster yellows are one of the most debilitating diseases that can infect coneflowers permanently. It’s caused by bacteria-like parasites called phytoplasma, which infect the coneflower’s sap. Leafhoppers usually spread these parasites as they travel from plant to plant, feeding on sap.

Symptoms of aster yellows include yellowing or reddening leaves and stunted growth. Strange green growths may also start emerging from the plant’s central cone. If aster yellows infect your coneflower, flower heads may not develop properly.

Aster yellows are difficult to combat and require targeting the leafhoppers that spread the disease. Keep the area around your coneflowers free of weeds and plant garlic, mint, or yarrow as companion plants to deter leafhoppers.

2) Fusarium Rot

Fusarium Rot affecting the green leaves of a garden plant

Fusarium rot is a fungal disease affecting coneflowers’ crowns and roots. It’s caused by the soil-borne Fusarium oxysporum fungus, which enters coneflowers through damaged parts of the plant.

The main symptom of fusarium rot is a strange wilting behavior shown by infected coneflowers. The flowers will wilt during the hotter part of the day before seemingly recovering at night. Other symptoms include stunted growth and yellowing lower leaves on one side of the plant.

To combat fusarium rot, avoid damaging coneflowers when dividing or transplanting them. Avoid watering too much, as waterlogged soil can exacerbate fusarium rot.

3) Leaf Spot

Leaf Spot

Various leaf spot diseases, such as Alternaria leaf spot, can afflict and kill coneflowers. Fungal diseases cause leaf spot and can even infect coneflower seeds. Leaf spot symptoms include brown or black spots on the leaves or unsightly lesions on the stems.

To defend your coneflowers against leaf spot, give them plenty of space so air can flow around the plant. Avoid overwatering the soil as fungal diseases like leaf spot love moist conditions. Before sowing, you can soak the seeds in a 1% bleach solution for five minutes.

4) Powdery Mildew

Powdery Mildew displaying patches of white across an otherwise green leaf

Powdery mildew affects a vast range of plants, including coneflowers. It’s another fungal disease that thrives in moist, humid conditions. Powdery mildew is easily identified by the dusty white powder that appears on the foliage of infected coneflowers.

If your coneflower is infected with powdery mildew, remove the affected foliage and reassess the plant’s growing conditions. Ensure that your coneflower has adequate space for good air circulation. Keep the plant somewhere sunny, and make sure to avoid overwatering.

5) Sclerotinia Stem & Root Rot

Sclerotinia Stem & Root Rot causing the decay of a green plant stalk

Sclerotinia stem and root rot is another fungal disease that can attack coneflowers. The disease is caused by Sclerotinia sclerotiorum and is prevalent in moist conditions. Some coneflower species, such as Echinacea purpurea or purple coneflower, are more resistant to the disease than others.

Infected coneflowers may display black or dark brown lesions towards the base of the stems near the top of the soil. Blotches and white growths resembling cotton wool may appear on the plant. Coneflowers will die back if sclerotinia stem rot runs its full course.

The best control method is providing good airflow and space around your coneflowers. Try to avoid overwatering as well.

6) Aphids

A cluster of tiny green Aphids crawling across the leaf of a green plant

Aphids are one of the main enemies of gardeners worldwide and can sometimes infest coneflowers. They appear as tiny black or green insects that feed on plant sap and are occasionally farmed by ants. Aphids congregate on the undersides of foliage, so you can spot them immediately.

Other symptoms of an aphid infestation include black mold on the leaves, misshapen yellow leaves, and stunted growth. Aphids can be evicted by spraying the underside of coneflower leaves with water from a hose. You can also use insecticides such as neem oil or insecticidal soap.

7) Eriophyid Mites

Tiny Eriophyid Mites nesting on a green leaf

Also known as gall mites, eriophyid mites are tiny insects invisible to the naked eye. These mites can infest coneflower flower heads, and the symptoms of an infestation can look similar to aster yellows disease. Deformed flowers on the central cone, bronzing or yellowing leaves, and strange lumps called galls are symptoms of eriophyid mites.

Although eriophyid mites can make your coneflowers look strange, they won’t kill the plant. If you want to eliminate them, use horticultural oils such as neem oil or insecticidal soaps.

8) Japanese Beetles

A single Japanese Beetle sits atop the center of a purple coneflower

Japanese beetles are a common summer pest that targets coneflowers. These ravenous beetles feed on both the flowers and foliage of coneflowers. They’re easily spotted thanks to their iridescent green carapaces.

If your coneflower’s leaves are peppered with holes, it’s probably suffering from Japanese beetles. Pick off any adults you find and squish them. Add biological control measures like nematodes to the soil to control the larvae.

9) Leafhoppers

A single Leafhopper laying on a green leaf

As mentioned earlier, leafhoppers can spread aster yellows disease to your coneflowers. If your coneflower shows signs of aster yellows disease, you’re dealing with leafhoppers.

Control these pests by regularly weeding around your coneflowers or planting companion plants that deter leafhoppers. Garlic, mint, and yarrow are all excellent choices for this. You can also encourage or bring in leafhopper predators such as assassin bugs.

10) Sweet Potato Whiteflies

A cluster of tiny Sweet Potato Whiteflies on a green leaf

Also known as silverleaf whiteflies, sweet potato whiteflies are an annoying pest that can attack your coneflowers. Like aphids, these insects hide on the underside of leaves and extract sap. Symptoms include black mold on the foliage and yellowing or shedding leaves.

Use insecticidal soap or neem oil to remove infestations. You can also try and encourage natural predators such as assassin bugs.


Pesticide and Insecticide Options and Solutions

A person spraying garden plants with an insecticidal solution

Although the pests and diseases that target coneflowers may seem daunting, they can be defeated. Plenty of insecticide and pesticide options are available; some can even be found in the grocery store. Always follow the instructions on the packet.

Horticultural Oils

Horticultural oils such as canola and neem oil are easy, cost-effective ways to combat coneflower pests. You can find canola oil in grocery stores and neem oil in garden stores. Both oils can eliminate pests such as aphids and disrupt their breeding cycles.

Insecticidal Soap

Insecticidal soap is geared towards eliminating pests that might infest your coneflowers. It works by dehydrating and suffocating the pests and breaking down their cells. Insecticidal soap is ideal for dealing with aphids, but you can also use a mix of dish soap and warm water.

Biological Controls

Biological controls are a form of pest control that uses predatory organisms to target specific pests. These controls usually come in the form of nematodes – microscopic animals such as tiny worms. Nematodes can help eliminate Japanese beetle larvae that may attack your coneflowers.

Pesticides

Chemical pesticides should be a last resort as they can contaminate the soil and affect biodiversity. Always try and use natural methods first or pick off insects like Japanese beetles and leafhoppers yourself. Pesticides can be used to destroy larger infestations of aphids and other pests.


Managing Pests and Diseases

The best way to manage or prevent pests and diseases that trouble your coneflowers is to provide good growing conditions. This keeps your coneflowers strong and healthy while minimizing the conditions that suit diseases. 

Coneflowers are pretty easy to grow and require little maintenance as long as they have a sunny, dry climate. They’re also relatively straightforward to transplant or divide if you need to relocate or want to expand your collection. 

Always provide plenty of space around your coneflowers to keep air circulating the stems, reaching 4 or 5 feet in height. This helps combat diseases like powdery mildew. Use well-draining chalky, loamy, or sandy soil to provide good airflow to the roots. Give your coneflowers a sunny spot with six to eight hours of direct light daily.

Try to avoid overwatering coneflowers, as this can exacerbate diseases such as fusarium rot. Mature coneflowers don’t need watering unless conditions are exceptionally dry. Young plants should only be watered once weekly for 6 to 12 months.

Coneflowers can also benefit from some light fertilizing during the flowering season and occasional deadheading, and it’s prudent to cut back coneflowers as we approach the end of fall. 


The Final Word

Coneflowers are symbolic, beautiful, hardy perennials that are great for beginners. However, they can suffer from diseases and pests like aster yellows, aphids, and Japanese beetles. Keep your coneflowers healthy by providing good growing conditions. If you spot pests or diseases, use horticultural oils, insecticidal soap, and biological control to eliminate the problem.

Contributing Editor | edd@petalrepublic.com | Full Bio

Edd is a budding content writer and gardener living in the United Kingdom. He has a bachelor's degree in Creative and Professional Writing and has written for several gardening publications online. He is passionate about nature and sustainability with a focus on gardening and wildlife.

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