Euonymus Diseases and Insect Pests in South Carolina

Quick Guide

Affected Plants: Japanese euonymus (Euonymus japonicus), wintercreeper (Euonymus fortunei), running euonymus (Euonymus obovatus), and other Euonymus species.
Primary Disease Types: Powdery mildew, crown gall, Cercospora leaf spot, anthracnose, and scab.
Primary Insect Pests: Euonymus scale (Unaspis euonymi).
Primary Causes: Fungal pathogens, bacterial infection, and armored scale insects.
Most Important Prevention Strategy: Grow euonymus in well-drained sites, avoid plant stress, improve air circulation, remove infected plant debris, and monitor regularly for scale insects.
Chemical Control: Fungicides and insecticides may be used when needed as part of an integrated pest management (IPM) program. Always read and follow all label directions.

Key Takeaways

• Powdery mildew is the most common disease affecting euonymus.
• Euonymus scale is the most damaging insect pest.
• Good sanitation and reducing plant stress prevent many problems.

Introduction

There are 60 different euonymus varieties available from American sources. They range from evergreen shrubs, such as Japanese euonymus (Euonymus japonicus), to evergreen vines, such as wintercreeper euonymus (Euonymus fortunei), to deciduous groundcovers, such as running euonymus (Euonymus obovatus).

All euonymus species prefer full sun or light shade and fertile, moist, well-drained soil. They do not tolerate waterlogged soil.

For more information on growing euonymus, refer to Euonymus (HGIC 1063).

Euonymus Diseases: Powdery Mildew on Euonymus

Powdery mildew is the most common fungal disease affecting euonymus and can reduce the ornamental quality of susceptible plants.

Cause

Powdery mildew is caused by the fungus Oidium euonymi-japonici.

Symptoms

Symptoms may include:

• Flat, white to gray growth on the upper surfaces of the leaves.
• White growth that can be partially rubbed off.
• Slight yellowing of leaves.
• Curled and scarred leaves on young shoots when infections are severe.
• Premature leaf drop may occur, but is not usually extensive.

For more information about powdery mildew, visit Powdery Mildew on Landscape and Garden Plants (HGIC 2049).

Prevention & Treatment

Several cultural practices can reduce powdery mildew on euonymus and improve overall plant health. Fungicides protect new foliage from infection but do not remove existing fungal growth.

Cultural Controls

• Prune and destroy heavily diseased branches.
• Remove and dispose of fallen leaves.
• Plant in full sun or light shade.
• Provide adequate spacing for good air circulation.
• Avoid overhead watering when possible.

Chemical Control

Begin fungicide applications before new foliage becomes infected. Fungicides protect foliage from infection (by killing the mildew spores as they germinate), but will not remove the dense, white fungal growth from infected leaves.

Active ingredients labeled for powdery mildew management include:

• Myclobutanil
• Propiconazole
• Thiophanate-methyl
• Sulfur
• Copper fungicides
• Horticultural oil (2% solution; 5 tablespoons per gallon of water)

Rotate fungicides with different modes of action when repeated applications are necessary to help reduce the risk of fungicide resistance.

See Table 1 for examples of products.

Always read and follow all pesticide label directions.

Euonymus Diseases: Crown Gall on Euonymus

Crown gall is a bacterial disease of euonymus that produces swollen galls on stems, roots, and the crown, reducing plant vigor over time.

Cause

Crown gall is caused by the soil-inhabiting bacterium Agrobacterium tumefaciens.

Symptoms

Symptoms may include:

• Large, corky galls at the base of the plant (crown)
• Galls developing on the stems and roots
• Rounded galls with rough, irregular surfaces
• Yellowing leaves
• Slowed or stunted growth
• Branch dieback
• Reduced water and nutrient movement caused by the galls

Prevention & Treatment

Once infected, euonymus plants cannot be cured. Management focuses on limiting the spread of the bacterium and maintaining plant health.

Cultural Controls

• Avoid introducing contaminated soil or infected transplants.
• Sterilize pruning tools with rubbing alcohol after each cut when removing infected branches.
• Prune affected stems below the gall to improve plant appearance.
• Destroy severely infected plants.
• Avoid replanting susceptible species in the same location for two to three years because the bacterium can survive in the soil.

Resistant Replacement Plants

When replacing infected euonymus, select resistant plants such as:

• Barberry
• Boxwood
• Elderberry
• Holly
• Mountain laurel

Chemical Control

No chemical treatment will cure crown gall on established euonymus plants.

Euonymus Diseases: Cercospora Leaf Spot on Euonymus

Cercospora leaf spot is a common fungal disease of euonymus that primarily affects leaf appearance but rarely poses a threat to established plants in South Carolina.

Cause

Cercospora leaf spot is caused by the fungi Cercospora destructiva and C. euonymi.

Symptoms

• Irregularly shaped brown leaf spots
• Spots range in size from pinpoints to ½ inch across
• Spots often merge to cover the whole leaf
• Grayish-tan centers in larger spots
• Tiny, black fungal fruiting bodies on the upper surface of older lesions (spots)

Prevention & Treatment

Cercospora leaf spot on euonymus is usually a cosmetic disease, but sanitation and timely fungicide applications can help reduce disease severity.

Cultural Controls

• Rake up and destroy fallen leaves.
• Remove infected plant debris to reduce fungal inoculum.
• Maintain good plant vigor by growing euonymus under recommended cultural conditions.

Chemical Control

If the disease is severe or recurring, apply a fungicide containing:

• Thiophanate-methyl

See Table 1 for example products

Always read and follow all directions on the label.

Euonymus Diseases: Anthracnose on Euonymus

Anthracnose is a fungal disease that affects the leaves and twigs of euonymus in South Carolina, especially during cool, wet spring weather.

Cause

Anthracnose is caused by the fungus Colletotrichum gloeosporioides.

Symptoms

Symptoms may include:

• Small brown leaf spots with light-colored centers
• Brown lesions on young twigs.
• Tiny cracks in the leaf spots indicate fungal fruiting structures.
• Premature leaf drop (defoliation) during severe infections.
• Greater disease susceptibility in variegated euonymus varieties.

Prevention & Treatment

Good sanitation combined with preventive fungicide applications can help reduce anthracnose severity, particularly during cool, wet springs.

Cultural Controls

• Rake up and destroy infected leaves and twigs.
• Prune out infected shoots as soon as symptoms appear, especially on smaller plants.

Resistant Varieties

Variegated euonymus varieties are more susceptible to anthracnose. When selecting plants, be aware that non-variegated varieties may be less prone to disease under favorable conditions.

Chemical Control

When anthracnose has been severe in previous years or environmental conditions favor disease development, preventive fungicide applications may be warranted.

Active ingredients include:

• Chlorothalonil
• Copper fungicide
• Mancozeb

See Table 1 for product examples.

Always read and follow all pesticide label directions.

Euonymus Diseases: Scab on Euonymus

Scab is a fungal disease that primarily affects Japanese euonymus, causing distinctive raised leaf and stem spots that reduce ornamental quality.

Cause

Scab is caused by the fungus Elsinoë euonymi-japonici.

Symptoms

Symptoms may include:

• Very small grayish-white spots on the upper and lower leaf surfaces.
• Spots that are most numerous on the upper leaf surface.
• Raised orange-cinnamon-colored, waxy margins around the spots.
• Raised, dark centers in larger lesions.
• Spots that merge together when infections are severe.
• Centers of some leaf spots fall out, creating a shot-hole appearance.
• Dark, irregular spots on stems that may merge together.

Prevention & Treatment

Good sanitation and timely fungicide applications can help reduce the spread of scab on susceptible euonymus plants.

Cultural Controls

• Rake up and destroy all fallen leaves.

Chemical Control

If scab has been a recurring problem, apply a fungicide containing:

• Thiophanate-methyl

See Table 1 for examples of products.

Always read and follow all pesticide label directions.

Euonymus Insect Pests: Euonymus Scale on Euonymus

Euonymus scale is the most common and damaging insect pest of euonymus in South Carolina, but several species of scale insects may be found on euonymus plants.

Identification & Life Cycle

Several scale species are pests of euonymus. Scales are unusual insects because they are small, immobile as adults and have no visible legs. Their appearance varies depending on species, age, and sex. They feed by piercing leaves or stems with their mouthparts and sucking plant sap.

Numerous white male euonymus scales (Unaspis euonymi) may almost cover the undersides of leaves. The females are larger and darker.

Key identifying characteristics include:

• Adult females have dark, oyster-shaped armored coverings about 1/16 inch long.
• Adult males are tiny, winged insects that emerge from narrow, white armored coverings.
• Yellow eggs are found beneath the female’s protective covering.
• Newly hatched crawlers are the only mobile immature stage before forming their own protective covering.
• Heavy infestations often have numerous white male scales on leaves and stems, making infestations easy to spot.

Symptoms

Symptoms may include:

• Yellow spots on the upper surfaces of leaves.
• White scale coverings clustered along leaf veins and stems.
• Declining plant vigor.
• Branch dieback.
• Death of heavily infested plants.

For more information about armored scales, visit Armored Scale Insects on Ornamental Plants in South Carolina (HGIC 2012).

Prevention & Control

An integrated pest management (IPM) approach that combines plant health practices, monitoring, and properly timed pesticide applications provides the best control of euonymus scale on euonymus.

Cultural Controls

• Select resistant cultivars when establishing new plantings.
• Scrape off light infestations by hand.
• Prune and dispose of heavily infested branches promptly.
• Maintain recommended fertility.
• Apply mulch around plants.
• Water weekly during drought to reduce plant stress.

Resistant Varieties

The following cultivars are reported to be resistant to euonymus scale:

• Euonymus alatus ‘Compactus’
• Euonymus fortunei ‘Acutus’

Biological Control

Natural enemies help suppress euonymus scale populations. Because broad-spectrum insecticides can reduce these beneficial insects, monitor infestations carefully and use contact insecticides only when crawler activity is confirmed.

Chemical Control

Horticultural Oils (also called supreme, superior, or summer oils)

Horticultural oils are among the most effective treatments for armored scales because they penetrate the waxy covering and smother eggs, crawlers, and adults.

Dormant applications

• Apply a 3% to 4% horticultural oil solution (7½ to 10 tablespoons per gallon of water) during winter through to early spring to target overwintering adults and eggs.

Growing season applications

• Apply a 2% horticultural oil solution (5 tablespoons per gallon of water) in late spring (April) when crawlers and newly settled scales with thin waxy covers are present.

For best results:

• Spray when temperatures are between 45°F and 85°F.
• Apply in the early evening to reduce the risk of plant injury and slow drying time.
• Repeat applications may be necessary.

Monitoring Crawlers

Adult scales are protected beneath their waxy coverings, but crawlers are susceptible to contact insecticides.

Monitor crawler emergence by using:

• Yellow sticky cards.
• Double-sided tape wrapped around infested branches.
• Infested shoots or leaves enclosed in a clear plastic bag to observe crawler movement.

Crawler emergence generally coincides with the flush of new plant growth in the spring, although overlapping generations may extend crawler activity in coastal areas.

Crawlers are often yellowish-orange and appear as moving specks of dust, making close inspection helpful when determining the proper timing for insecticide applications.

Contact Insecticides

When crawler activity has been confirmed, products containing the following active ingredients may be used:

• Acephate
• Bifenthrin
• Cyfluthrin
• Cyhalothrin
• Malathion

Apply three applications at 10-day intervals, following all label instructions and precautions.

See Table 1 for example products.

Systemic Insecticides

A spring soil application of dinotefuran around the base of the plant can improve control of armored scales and may be used in combination with horticultural oil applications.

See Table 1 for product examples.

Note: Soil-applied products containing imidacloprid do not effectively control armored scales, such as euonymus scale.

Always read and follow all pesticide label directions.

Fungicide and Insecticide Products for Home Landscape Use on Euonymus (Table 1)

The following products contain active ingredients labeled for managing diseases and euonymus scale on home landscape euonymus. Product availability may change over time, and inclusion does not imply endorsement by Clemson Extension.

Fungicides

Active Ingredient	Example Product Names
Chlorothalonil	Bonide Fung-onil Multi-purpose Fungicide Concentrate Bonide Fung-onil Multi-purpose Fungicide Ready to Use Ferti-lome Broad Spectrum Landscape & Garden Fungicide GardenTech Daconil Fungicide Concentrate GardenTech Daconil Fungicide Ready-to-Use Hi-Yield Vegetable, Flower, Fruit And Ornamental Fungicide Ortho MAX Garden Disease Control Concentrate Southern Ag Liquid Ornamental and Vegetable Flowable Fungicide Tiger Brand Daconil
Copper Fungicide	Bonide Captain Jack’s Liquid Copper Fungicide Bonide Copper Fungicide Spray or Dust Ready to Use Camelot O Fungicide/Bactericide Monterey Copper Fungicide Garden Spray Liqui-Cop Natural Guard by ferti-lome Copper Soap Fungicide Concentrate Natural Guard by ferti-lome Copper Soap Fungicide Ready to Use Southern Ag Liquid Copper Fungicide
Myclobutanil	Ferti-lome F-Stop Lawn & Garden Fungicide Monterey Fungi-Max Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate For Gardens
Propiconazole	Banner Maxx II Fungicide Bonide Infuse Systemic Disease Control Bonide Infuse Systemic Disease Control Lawn & Landscape Ready to Spray Ferti-lome Liquid Systemic Fungicide II Quali-Pro Propiconazole 14.3 Fungicide
Sulfur	Bonide Sulfur Plant Fungicide Micronized Spray or Dust Ready to Use Hi-Yield Snake Eyes Brand Dusting Wettable Sulfur Safer Brand Garden Fungicide For Flowers, Fruit And Vegetables Concentrate Safer Brand Garden Fungicide II For Flowers, Fruit And Vegetables Southern Ag Wettable or Dusting Sulfur
Thiophanate Methyl	Southern Ag Thiomyl Systemic Fungicide

Insecticides

Active Ingredient	Example Product Names
Acephate	BioAdvanced Science-Based Solutions 2-in-1 Systemic Rose & Flower Care Granules with 6-9-6 Fertilizer Bonide Systemic Insect Control II
Bifenthrin	Hi-Yield Bug Blaster Bifenthrin 2.4 Ready to Spray Hi-Yield Bug Blaster II Bifenthrin 2.4 Ready to Spray Monterey Mite & Insect Control Monterey Mosquito Control Martin’s FLEE Ready to Use Yard Spray Ortho Outdoor Insect Killer Concentrate Ortho Bug B Gon Insect Killer for Lawns & Gardens1 Ortho BugClear Insect Killer for Lawns & Landscapes Bifen I/T Talstar P Professional Insecticide Up-Star Gold Insecticide Hi-Yield Vegetable & Ornamental Insect Control Granules Bonide Eight Insect Control Flower & Vegetable Above & Below Soil Insect Granules
Cyfluthrin	BioAdvanced Science-Based Solutions 24 Hour Lawn Insect Killer Ready-to-Spray BioAdvanced Science-Based Solutions Complete Brand Insect Killer for Soil & Turf Ready-to-Spray I BioAdvanced Science-Based Solutions Insect Killer for Lawns Ready-to-Spray BioAdvanced Science-Based Solutions Rose & Flower Insect Killer Ready-to-Use
Cyhalothrin	Bonide Eight Insect Control Garden & Home II Ready to Use Cutter Backyard Bug Control Spray Concentrate Cyzmic CS Controlled Release Insecticide Martin’s Cyonara Lawn & Garden Insect Control Martin’s Cyonara Lawn & Garden Insect Control Ready-to-Spray Spectracide Triazicide Insect Killer for Lawns & Landscapes
Dinotefuran	Gordon’s Zylam Liquid Systemic Insecticide Valent Safari 20 SG Insecticide
Horticultural Oil	Bonide All Seasons Horticulture Spray Oil Ready-to-Use Bonide All Seasons Horticulture & Dormant Spray Oil Ready-to-Spray Ferti-lome Horticultural Oil Spray Monterey Horticultural Oil Concentrate Monterey Horticultural Oil RTU Safer Brand Horticultural & Dormant Spray Oil Concentrate Southern Ag Parafine Horticultural Oil Summit Year-Round Spray Oil
Malathion	Bonide Malathion 50% Insect Control Gordon’s Malathion 50% Spray Hi-Yield 55% Malathion Insect Spray Martin’s Malathion 57% Ortho Max Malathion Insect Spray Concentrate Southern Ag Malathion 50% EC Spectracide Malathion Insect Spray Concentrate Tiger Brand 50% Malathion

RTS = Ready to Spray (a hose-end sprayer bottle)
RTU = Ready to Use (pre-mixed spray bottle)

Pesticide Disclaimer

Pesticide information is updated periodically, and product availability may change.

Always read and follow all label directions, precautions, and restrictions before purchasing, mixing, or applying any pesticide.

Mention of trade names is provided for informational purposes only and does not imply endorsement by Clemson Extension.

Consult the product label to confirm that the ornamental plant and target pest or disease are listed before use.

Pesticides are updated annually. The last updates were made on 7/26 by N. Jordan Franklin.

Originally published 03/00