- Euonymus Scale
- Euonymus Scale – Shrubs
- Appearance and Life Cycle
- Cultural Control
- Biological Control
- Chemical Control
- Dormant Spray
- Additional Resource
- Connecticut State The Connecticut Agricultural Experiment Station
- Problems of Japanese Euonymus
- Euonymus Scale Treatment – Tips For Controlling Euonymus Scale Bugs
- Euonymus Scale Treatment
- Controlling Euonymus Scale Bugs
- Euonymus Scale
- Unaspis euonymi (Comstock)
- Life History
- Treating Euonymus with Scale
- Euonymus Diseases & Insect Pests
- Insect Pests
- Diseases of the Euonymus Shrub
- Powdery Mildew
- Crown Gall
- Cercospora Leaf Spot
High populations of Euonymus scale can cause leaf loss and twig death.
Phil Pellitteri, UW Insect Diagnostic Lab, UW-Extension
Item number: XHT1153
Euonymus scale is a non-native scale that attacks evergreen shrub and vine forms of Euonymus (e.g., wintercreeper). In addition, this insect attacks privet, bittersweet and pachysandra.
Appearance: Euonymus scale females grow up to 1/16 inch in length, are brown and are shaped like tiny oyster shells. Euonymus scale males are smaller than females, white and elongated.
Symptoms and Effects: Euonymus scales feed on plant sap. Feeding damage first appears as yellow spots on leaves. When infestations are heavy, scales encrust leaves and branches, with feeding damage causing defoliation and branch dieback.
Life Cycle: Euonymus scale has two generations per year in Wisconsin. Eggs are protected under female scales and hatch in early June. The immature stages of the insect are called nymphs and an early mobile nymph stage is called the crawler stage. Nymphs are active over a period of a few weeks, and develop into adults after four to five weeks. A second generation of scales is produced in late July and August. This second generation matures, and the adults overwinter.
Control: Euonymus scale can be difficult to control. Heavily infested branches should be removed. Spray insecticides containing carbaryl, cyfluthrin, horticultural oil, insecticidal soap, malathion, or permethrin can be used for control of the crawler stage of Euonymus scale. Adults are protected from these insecticides by their scale coverings, and only young crawlers can be killed with spray treatments. Therefore, spray treatments should be started in early June, and three applications made at 10 to 12 day intervals are needed to achieve control. Thorough coverage of both the upper and lower leaf surfaces is required for spray insecticides to be effective.
Systemic insecticides such as imidacloprid can also be used for control. However, while these products reduce scale populations, they typically do not provide 100% control of Euonymus scale on woody plants. Imidacloprid-containing insecticides are used as soil drenches and should be applied in the fall.
Finally, two parasitic wasps and two predatory beetles have been introduced into the US to help control Euonymus scale. The lady beetle Cybocephalus nipponicus can be purchased by homeowners and released to aid in control.
Tags: insect, pest, scale Categories: Tree & Shrub Problems
Euonymus Scale – Shrubs
Male scale covers. Photo credit – J. Davidson, UMD
The Euonymus Scale (Unaspis euonymi) is a very common and serious pest of evergreen euonymus, especially Euonymus japonica. Infestations can also been found on pachysandra. This armored scale insect develops large populations and is very difficult to control. Like most armored scales, individuals form a tough cover of waxes and proteins which they enlarge as they grow.
Appearance and Life Cycle
The male scale covers are elongate and white with three longitudinal ridges. They occur in greatest numbers on the lower branches and leaves of the plant. The female scale covers are broadly oystershell-shaped and dark brown. They are found mainly on stems, and only occasionally on leaves. They are about 1-2 mm (1/16 inch) long. The eggs are deposited under the female scale cover and begin hatching in May. The young scales, called crawlers, appear as yellow specks smaller than a pinhead. The crawlers move to leaves or stems and begin feeding by piercing the plant tissue with thin, threadlike, microscopic mouthparts. They quickly begin producing the hard protective covering which they extend backward as they grow. There are two generations of Euonymus Scale produced in Maryland. The hatching time of the second generation is not clear-cut, however, and the two generations overlap. All stages are present in the summer, but crawlers are most abundant in May and July.
Conspicuous white flecks on plant leaves are the best signal that this pest is present. On young green leaves, each white fleck often is surrounded by a yellow halo. Heavily infested susceptible plants will prematurely drop large numbers of leaves in the winter and dieback will occur. Dieback is most serious in winters following droughts.
Avoid planting Euonymus japonica because it is highly susceptible to this scale. Plant vigorously growing varieties such as Euonymus kiautschovica ‘Manhattan’ that can better tolerate leaf drop. Less vigorous varieties such as those which are variegated and dwarfed should be mulched and watered adequately during a drought to reduce winter leaf loss. Where possible, heavily infested Euonymus shrubs and hedges should be cut to the ground and the new shoots protected from reinfestations by sprays as needed. Over-fertilization increases scale insect populations.
An imported species of lady beetle, Chilocorus kuwanae, has been successfully established in Maryland to help control this pest. This round, 1/5″ wide, black beetle has two red spots on its’ back. Both the adult and the immature stages of this beetle have a hearty appetite for all stages of Euonymus Scale and research has shown that the can control infestations. When adults of this beetle move to new plants they can bring with them a small mite (Hemisarcoptes malus) that also feeds on the scales. Chemical sprays should only be applied to infested plants that do not have lady beetles on them. In this way, the beneficial insects present will not be eliminated from the entire planting. Horticultural oil sprays cause the least reduction in lady beetle populations.
Dormant sprays with horticultural oil, and summer sprays with oil or insecticides will help control the Euonymus Scale. Spray all parts of the plants thoroughly. Spray the summer rate of horticulture oil when the crawlers (young scales) are present in May through June and then again in late July through September.
Spray in early spring before new growth starts.
Q: 1. My variegated euonymus has lots of little white dots under the leaves and it doesn’t look very healthy. Can you diagnose?
Q: 2. I have a row of golden euonymus shrubs that have developed scale on the leaves and a few of the short stems. If I cut the back the foliage drastically now, will this harm the shrubs?
A: In my experience, a heavy infestation of scale on euonymus is almost impossible to control without pruning to remove the majority of the leaves and insects first.
Euonymus grows vigorously, so pruning moderately in winter won’t hurt it terribly. You’ll get regrowth in spring and summer.
If your shrub is heavily infested, consider removing it and replacing with a holly or other plant.
If your shrub is only lightly infested, you can try the chemical route.
I recommend applying systemic insecticide in spring and also spraying what’s left of the shrub (after pruning) with three times per year (April, June, January). Be sure to follow label directions for hot weather application.
Also see Euonymus Scale
Tags For This Article: euonymus, insects, pruning
Connecticut State The Connecticut Agricultural Experiment Station
Plant Health Problems
Diseases caused by Fungi:
Powdery mildew, Microsphaera euonymi and M. penicillata.
Powdery appearance of leaves indicates presence of one of these fungi. Infection is favored by hot humid weather.
Control of this disease is usually not necessary since symptoms develop late in the season.
Anthracnose, Colletotrichum gloeosporioides.
Brown to black lesions on the leaves are indicative of anthracnose. Lesions may occur on the stem, and portions of the plant distal to stem lesions frequently die back.
Management of this disease includes raking and removing fallen leaves and pruning to remove stem cankers. Control can also be achieved with the use of fungicides when applied before symptoms are severe. Among compounds registered for use in Connecticut are chlorothalonil and thiophanate-methyl. New research indicates that the fungus may become resistant to copper, so copper-containing compounds should be used on a limited basis, to prevent or delay development of resistance. Consult the label for dosage rates and safety precautions.
Diseases caused by Bacteria:
Crown gall, Agrobacterium tumefaciens.
Roots and running stems may show galls of considerable size. If infection is heavy, plants may be destroyed.
If there are only a few galls, affected stems may be removed. Pruning tools should be disinfected by dipping in dilute alcohol or dilute bleach (a solution of 10% bleach in water) between cuts. New varieties that are more resistant to crown gall are available and should be utilized.
Aphids, Aphis fabae.
The bean aphid occurs on euonymus. There are many generations each year. Eggs are laid in the autumn. They overwinter on various shrubs. For more detail and control measures, see the Aphid fact sheet.
Black vine weevil, Otiorhynchus sulcatus.
The larvae of this weevil often injure Euonymus plants, especially the wintercreeper varieties, in nurseries and ornamental plantings by feeding on the roots. The small grubs devour the small roots and progress to chewing the bark from the larger roots, often girdling them. The tops of girdled plants first turn yellow, then brown, and the severely injured plants die. Large landscape plants tolerate root grazing quite well, but leaf notching by adults can be unsightly. The 1/2″ long adult weevil is black, with a beaded appearance to the thorax and scattered spots of yellow hairs on the wing covers. Only females are known, and the adults are flightless. They feed nocturnally, notching the margins of the foliage. The legless grub is white with a brown head and is curved like grubs of other weevils. Adults and large larvae overwinter, emerging from May – July. The adults have to feed for 3-4 weeks before being able to lay eggs. Treating the soil with insect pathogenic nematodes may control the larvae and should be the first line of defense for landscape plantings. Acephate and fluvalinate are among the compounds registered for control of this pest in Connecticut, and should be applied when there is adult feeding and before egg laying starts. The usual timing for these foliar sprays is during May, June and July at three week intervals. Insecticide resistance is very common; be aware that adults may appear to be dead following contact with fluvalinate, but may recover from poisoning within a few days. Consult the labels for dosage rates and safety precautions.
Cottony maple scale, Pulvinaria innumerabilis.This scale infests euonymus. This is a brown, oval, soft scale on the stem in winter, but in June the large egg masses are formed, and their wax covering resembles a tuft of cotton. The young crawl in July and some of them live for a time on the leaves, but return to the twigs to pass the winter.
Among the compounds registered for use against this pest in Connecticut are horticultural oil, imidacloprid and diazinon. The best means of control are a dormant horticultural oil spray applied in early spring or imidacloprid applied as a systemic to be taken up by the roots. Diazinon sprays in early July will control the young crawlers. Consult the labels for dosage rates and safety precautions.
Euonymus scale, Unaspis euonymi.
This is perhaps the most serious pest of euonymus, and it often kills entire branches. It also infests bittersweet and pachysandra. The female shells are gray and pear-shaped, and the male shells are smaller, narrower, and whiter. There are probably two generations each season, and the winter is passed in a nearly mature condition; eggs are formed during May and hatch later in the month. All badly infested and injured branches may be cut and burned. Among the compounds registered for control of this pest in Connecticut are horticultural oil, insecticidal soap and malathion. Spraying with ultrafine horticultural oil, either in mid-April for a dormant treatment or early June and again in mid-July, will control this scale while conserving the natural predators and parasites that might be present. Sprays of insecticidal soap and malathion applied in early June and again in mid-July will also control this scale. Consult the label for dosage rates and safety precautions.
San Jose scale, Quadraspidiotus perniciosus.
Large infestations of the San Jose scale can cause branch and even shrub death. Partially-grown scales overwinter under their circular gray covering or scale on the twigs and the branches of trees. They begin to feed as the sap starts to flow. When apple trees bloom, the males emerge from under their scales to mate with the immobile females. Females are circular and cone-shaped, and their circular scales are about 1/16″ in diameter, with a raised center or nipple. The males are smaller and elongate, with the nipple not centered on the scale. Females give live birth to tiny bright yellow crawlers in June. The young crawlers quickly settle, insert their long mouthparts into the twigs, and then suck sap from branches. As they grow, the crawlers secrete a waxy filament that becomes their scale or covering. Overlapping generations are present from June through September. Scales may be controlled by applying horticultural oil at a dormant timing or in June when crawlers are active. Diazinon, which is among the compounds registered for control of this pest in Connecticut, may also be applied against the crawlers in June. Consult the labels for dosage rates and safety precautions. To detect the yellow crawlers, wrap black tape coated with Vaseline around small branches. Adult flights may be detected with pheromone traps.
Twospotted spider mite, Tetranychus urticae.
This pest infests the undersides of the leaves, especially of the burning bush varieties, which become light yellow in color, and the plants have a generally unhealthy appearance. Sometimes the mites form webs, which more or less enclose the upper as well as the lower leaf surface. Among the compounds registered for control of this pest in Connecticut are insecticidal soap and ultrafine horticultural oil. Spraying with insecticidal soap will give sufficient control if applied at least twice at 7-10 day intervals. The predatory mite, Neoseiulus fallacis, is most commonly found feeding where there are mite infestations. A single application of ultrafine horticultural oil (1/2 to 1% dilution) can be effective if predatory mites are present. Special care should be taken with soap or oil to obtain thorough spray coverage, because they only work on contact. Abamectin is an effective restricted use product. Consult the labels for dosage rates and safety precautions. Avoid applying carbaryl or pyrethroids, which tend to be much more toxic to the predators than to the pest spider mites.
There really is no “treatment” for plants infected with crown gall. Once the symptom i.e. the gall shows up, it is too late to treat even if there were antibiotics available for the purpose. So, the main control options rely primarily on preventing the infection in the first place.
1. Prune Off Infected Galls – To make the plant look better, you can cut off and destroy the infected stems below where the gall has formed. Sterilize the pruning shears with a one part bleach to nine parts water solution between cuts and before moving to prune other plants.
2. Destroy Infected Plants – Remove and destroy (burn or send to the dump) infected plants. Since the bacterium stays in the soil for years, replace it only with a plant species known to be resistant.
3. Sterilize the Soil – Commercial nurseries have potent chemicals known as soil sterilants available to them but, unfortunately, these are not used in home landscape situations.
4. Exclude the Problem – Purchase plants from reputable nurseries only. If someone wants to give you a plant, be sure to closely inspect them for any signs of galls.
5. Plant Resistant Species – Several landscape plants appear to have a high degree of resistance to bacterial crown gall. These would include barberry, hornbeam, true cedars, ginkgo, golden raintree, tulip tree, mahonia, spruce, linden, boxwood, Catalpa, beech, holly, larch, Magnolia, black gum, pine, Douglas fir, bald cypress, hemlock, birch, firethorn, redbud, smoke tree, sweet gum, deutzia, serviceberry, yellowwood, yew, and zelkova.
Problems of Japanese Euonymus
Foliage Damaged In Winter due to Wind Chill
Severe wind chill may damage the foliage during the winter but euonymus shrubs usually regenerate themselves every spring. Some variegated forms may revert to green if they experience a severe wind chill. This problem can be controlled somewhat by surrounding shrubs with protective material such as burlap or agricultural fleece. If wind is an annual problem, move the plant to a more protected location on the north or east sides of the house.
Leaves and Stems Covered With Small Bumps means Scale Insects
Scale insects form groups of small bumps or blister-like outgrowths on stems and leaves. These are waxy shells that protect the insect beneath as it feeds. The shells may be white, yellow or brown to black, and are about 1/25 to 1/50 inch in diameter. Scale is the nemesis of evergreen euonymus and other members of the euonymus family. The first sign of a scale attack is often discoloration of upper leaf surfaces, followed by leaf drop, reduced growth, and stunted plants. Heavy infestations kill winter creepers. Some scale species secrete honeydew, which coats foliage and encourages ants and sooty molds. Scale outbreaks can be triggered by pesticides used against other pests or by environmental stresses such as too much or too little water. Over fertilizing may encourage lush growth susceptible to scale attack.
Scrape minor scale infestations off plant surfaces with a fingernail, or use a cotton swab dipped in rubbing alcohol. Spray heavily infested plants with a mixture of alcohol and insecticidal soap every 3 days for 2 weeks. Add 1 tablespoon of alcohol to a pint of ready to use commercial insecticidal soap spray. To prevent scale, spray dormant plants with a “superior” type oil in late winter or early spring. Apply insecticides when the young larvae (or “crawlers”) have hatched and before they start forming their new scales.
For more information see file on Controlling Scale.
Foliage Curls, Turns Yellow indicates Aphids
Aphids are soft-bodied, pear-shaped, green, brown, black, or pinkish insects a little bigger than the head of a pin. They cluster on tender new growth and suck sap from leaves and stems, causing foliage to curl, pucker, and yellow, and reducing the plant’s vigor. Ants, attracted by the aphids’ honeydew secretions, wander over the plants and protect the pests from natural enemies. Check leaf undersides for small groups of aphids. For light infestations, spray the undersides of the euonymus leaves vigorously with water three times, once every other day, in the early morning. In cases of heavy infestation spray visible aphids with insecticidal soap every 2 to 3 days. As a last resort, spray them with pyrethrum spray.
For more information see file on Controlling Aphids.
Leaves Discolored due to Thrips
Adult thrips are tiny, slender insects, 1/25 inch long, variously colored pale yellowish, black or brown. They rasp leaves and petals, sucking sap from the injury. Leaf surfaces become flecked and whitened and the tips wither, curl up and die. Leaf undersides are spotted with tiny black specks of excrement. Since thrips quickly burrow out of sight deep between petals, early identification and control is essential. Set out yellow sticky traps about 4 weeks after last frost as early warning devices. As soon as you spot thrips on the trap, spray insecticidal soap on nearby euonymus every three days for two weeks.
For more information see file on Dealing with Thrips.
Tumor-like Swellings on Roots, Trunk or Branches. Means Crown Gall
A bacterium sometimes infects euonymus shrubs through wounds and stimulates cells to form tumor-like swellings (galls) with irregular rough surfaces. To avoid crown gall, avoid planting euonymus plants that have galls on the roots or stems. Destroy heavily infected plants. If only a few galls are present, cut off and destroy the affected stems. Sterilize pruning tools afterward in 70% denatured alcohol to avoid spreading the disease.
Sunken Spots On Leaves indicates Anthracnose
This fungal disease forms distinct lesions on euonymus leaves, which appear as moist, sunken spots with fruiting bodies in the center. Leaf spots may run together, resembling a blotch or blight. The dead areas follow the veins or are bounded by larger veins. Sometimes the tips of branches die back to several inches below the buds. Pustules containing pinkish spores appear. Dieback and defoliation may occur in severe cases. Gather and destroy infected fallen leaves. Prune away diseased branches. Maintain plant vigor by feeding and watering well, especially during droughts. Spray with a copper fungicide such as Bordeaux mixture.
For more information see file on Controlling Fungal Disease.
Leaves Spotted, Turn Brown, Drop Prematurely due to Leaf Spot
Leaf spot diseases caused by various fungi occasionally attack euonymus, causing yellow, brown or black dead blotches on their leaves. Often these spots come together to form larger patches of dead tissue. Gathering and destroying fallen leaves usually controls this disease. If needed, spray the vine with a copper fungicide.
For more information see file on Controlling Fungal Disease.
Leaves Covered With White Powder means Powdery Mildew
Powdery mildew caused by fungi sometimes attacks euonymus, especially in the southern states and the Pacific coast. Spray affected shrubs thoroughly with wettable sulfur once or twice at weekly intervals starting as soon as you see the whitish fungus coating the leaves. Collect and discard all above ground refuse in the fall.
For more information see file on Controlling Fungal Disease.
Foliage Burned indicates Dogs.
Dog urine may discolor euonymus foliage and even kill branches. Spraying foliage with an anti transpirant gives some protection. Screen the plants or spray them with an aerosol pet repellant. For more information see the file on Dogs and Cats
Euonymus Scale Treatment – Tips For Controlling Euonymus Scale Bugs
Euonymus is a family of shrubs, small trees, and vines that is a very popular ornamental choice in many gardens. One common and sometimes devastating pest that targets these plants is the euonymus scale. Controlling euonymus scale bugs can be relatively simple and effective, as long as it’s done properly. Keep reading to learn more about how to get rid of euonymus scale.
Euonymus Scale Treatment
The first step in euonymus scale treatment is figuring out if you have an infestation. So what does euonymus scale look like? Euonymus scale bugs go through a few stages of life, during most of which they’re too small to spot easily. You’re more likely to know you have an infestation when you see white to yellow blotches on the tops of the plant’s leaves.
If the infestation is really bad, the plant may appear water stressed with leaves yellowing, drooping, and even falling
off. The bugs themselves are most visible in their late life scale stage, when they settle in on a single spot on the plant and grow a hard protective shell (a scale) over their backs. The larger female scales are about 2 mm long, brown, and shaped like an oyster shell. The scale insects may also appear like clusters of rice on plant leaves.
If you notice scales on your plant, scrape at a few with your fingernail. If you see an orange smear, the scales are still alive and need to be dealt with. If the scales simply crumble away dryly, all you have is the leftover shells of dead bugs and you don’t need to treat.
Controlling Euonymus Scale Bugs
Euonymus scale treatment is a game of timing. A population of scale on euonymus shrubs can go through to 2 to 3 generations in a single summer. The best time for euonymus scale treatment is when they’re in their crawler stage, before they grow their protective shells. This usually happens in spring to early summer.
Though they’re very small, you can see the crawlers as tiny yellow grubs on the leaves. During this time, you can spray with an insecticide or horticultural oil. If you miss this crawler stage, another should occur 6 weeks later.
A more organic form of treatment is the introduction of lady beetles, natural predators of euonymus scale, as well as pruning of heavily infested branches.
Certain horticultural oils can also be used when the scales are in their shells because it forms a layer that literally suffocates them. Read the label of your oil to see if it will be effective on mature scales.
Unaspis euonymi (Comstock)
The euonymus scale is a key pest of deciduous and evergreen euonymus, Euonymus spp., pachysandra, Pachysandra spp., and bittersweet, Celastrus spp. Vine-type euonymus are extremely susceptible to attack by this scale. This armored scale insect is native to Japan and China. It is now established in the United States and Canada.
The male’s white, narrow, waxy cover is about 0.8 mm long (Fig. 1a). Adult males emerge as tiny wasp-like insects. The waxy cover of a mature female is approximately 2 mm long, grayish-brown, flattened, and pear-shaped (Fig. 1b). The crawler stage of this key pest is about 0.3 mm long and yellowish-orange.
Figure 1. Adult euonymus scale waxy cover (a. male; b. female)
This armored scale overwinters as fertilized females. They begin laying eggs beneath their protective cover in late April and May. Eggs hatch over a 2-3 week period into first instar nymphs called crawlers. The crawlers wander over the bark and foliage for a short time, settle, and then begin to feed. Four to six weeks are usually required to complete development to adults. Males feed and develop under their waxy covers, mate with the females, and die. A second generation of crawlers is produced during late July through August.
This key pest causes injury to host plants by removing fluid from non-vascular plant cells. It does this with its piercing-sucking mouthparts that results in a reduction of plant health and yellowish stippling or spotting of the foliage. Heavy infestations may occur on twigs or leaves that can cause defoliation of the plant. An infestation of this armored scale may result in twig dieback or death of the plant.
This pest is most difficult to effectively manage at the base of infested plants near the ground. This is especially true with various vine types of euonymus.
To reduce populations of first generation crawlers, apply a registered insecticide according to label directions during late May through June. Second generation crawlers should be managed with applications made during late July through August. Prune and destroy heavily infested branches or twigs when indicated.
The lady beetle, Chilocorus kuwanae, was introduced several years ago in the eastern United States to assist with the management of euonymus scale. This lady beetle is 3- 4.5 mm long, black with two red spots on its wing covers.
Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.
Authored by: Gregory A. Hoover, Sr. Extension Associate
Revised November 2003
Treating Euonymus with Scale
It sounds like you have done all the right things, but your timing may have been off. You need to spray in the spring when the “crawlers” are out, usually around June (but I would look for them as early as May). To check for crawlers, hold a white sheet of paper under a branch and tap the branch vigorously. The crawlers will fall onto the paper. They are very small, so if you see these small “dots” moving around, then you know they have hatched. That’s the time to spray with the oil treatment. If you don’t catch them at that time, a spray will not work as they exude a waxy substance which covers them and protects them from outside elements. Then the systemic applications would be called for. If you catch the crawlers early, you should be able to avoid the scale from showing up later in the summer.
This is something I copied from a website which is very informative on the subject:
Euonymus scale, Unaspis euonymi, is an armored scale that is a very common pest of euonymus and pachysandra. Although the individual insects are small, infestations are often dense and plainly visible. Euonymus scale is now established in the United States and Canada and has become a major concern in many landscapes. Without treatment, heavy scale infestations will reduce photosynthesisthe process by which plants make “food” for themselves. This process involves sunlight, water and carbon dioxide., stunt plants, cause leaves to fall off, and kill all or part of the plants. Management of euonymus scale with contact insecticides may be difficult because of the waxy covering that protects the insects most of their lives. Newly hatched crawlers are the easiest to control with contact insecticides. Monitoring for scale crawler emergence is important to create an effective management program. Examine individual trees by tapping a branch over a white sheet of paper and looking for crawlers during the period when crawlers are expected. A soil-applied systemic insecticidea chemical compound designed to kill insects, can be either contact (kills on direct contact with the insecticide) or systemic (absorbed within a tree to kill insects when they try to feed on it), is effective for season long control of euonymous scale if applied in the spring. Moving through the plant where the insect feeds, a systemic insecticide eliminates the need for multiple sprays and constant monitoring, making treatment more manageable. Eggs are laid in early spring and hatch in late May or early June. The young nymphs crawl to other parts of the host plant before settling down to begin feeding. Once settled, they secrete their waxy protective covering and produce a second generation by mid-July, and a third generation in October.
Hope this was helpful. Feel free to contact us again if you have further questions.
Euonymus Diseases & Insect Pests
There are 60 different forms of euonymus available from American sources. They range from evergreen shrubs, such as Japanese euonymus (Euonymus japonicus), to evergreen vines, such as wintercreeper euonymus (E. fortunei), to deciduous groundcovers, such as running euonymus (E. 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 HGIC 1063, Euonymus.
Powdery Mildew: Powdery mildew is the most common and possibly the most difficult disease to control on euonymus. It is caused by the fungus Oidium euonymi-japonici. Symptoms consist of a flat, white to gray growth primarily on the upper surfaces of the leaves, which can be partially rubbed off. Leaves may yellow slightly and drop, but heavy leaf drop is not a characteristic symptom. On young shoots leaves can become curled and scarred if infection is severe.
Prevention & Treatment: Prune and destroy heavily diseased branches. Remove and destroy fallen leaves. Plant in a sunny area, do not crowd plants, and avoid overhead watering. Chemical applications should begin before new foliage is infected. Fungicides will protect foliage from infection (by killing the mildew spores as they germinate) but will not remove the dense, white fungal growth from infected leaves. Myclobutanil, propiconazole, and thiophanate-methyl have foliar systemic properties and can be sprayed less often than sulfur, copper fungicides, or horticultural oil. Mix horticultural oil at a 2% solution with water (5 tablespoons per gallon of water) to control powdery mildew. See Table 1 for examples of products. When powdery mildew persists and sprays are repeated, it is recommended to rotate fungicides to decrease the chance of fungi developing resistance. Read and follow all directions on the label.
Corky textured crown gall on wintercreeper euonymus (Euonymus fortunei).
Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, www.forestryimages.org
Crown Gall: Crown gall is caused by the soil-inhabiting bacterium Agrobacterium tumefaciens. Large, corky galls up to several inches in diameter appear at the base of the plant and on the stems and roots. The galls are rounded, with a rough, irregular surface. Plants with numerous galls are weakened, their growth is slowed, and leaves turn yellow. Branches may die back. The galls disrupt the flow of water and nutrients to the top of the plant.
Prevention & Treatment: The bacteria are spread by infested soil, transplants, and contaminated tools. Even though infected plants cannot be cured, they usually survive for many years. To improve the appearance of the plant, prune out and destroy affected stems below the galled area. Sterilize pruning shears after each cut with rubbing alcohol. Destroy severely infected shrubs. The bacteria will remain in the soil for two to three years. If you wish to replace the shrub, plant only resistant species of plants, such as barberry, boxwood, holly, mountain laurel, and elderberry.
Cercospora leaf spot on Japanese euonymus (Euonymus japonicus).
Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, www.forestryimages.org
Cercospora Leaf Spot: The fungi Cercospora destructiva and C. euonymi cause irregularly shaped brown spots on the leaves. The spots vary in size from pinpoints to half an inch across. They often merge to cover whole leaves. The centers of large spots become grayish tan and the causal fungus produces tiny, black fruiting bodies on the upper surface of the spots.
Prevention & Treatment: Leaf spot is fairly common but rarely life-threatening to the plant. Rake up and destroy all fallen leaves. Spray diseased plants with thiophanate-methyl. See Table 1 for examples of products. Read and follow all directions on the label.
Anthracnose: Anthracnose is caused by the fungus Colletotrichum gloeosporioides. Symptoms consist of small, brownish spots with light-colored centers on the leaves and twigs. Tiny cracks in the leaf spots indicate fruiting structures of the fungus. Considerable defoliation can result. The disease is a problem during cool, wet springs. Variegated varieties are more susceptible.
Prevention & Treatment: Rake up and destroy leaves and twigs from infected plants. On smaller plants, prune off and destroy all infected growth at the first sign of infection. Severe outbreaks may be prevented with periodic applications of chlorothalonil, mancozeb or copper fungicide sprays. See Table 1 for examples of products. Read and follow all directions on the label.
Scab: This disease, caused by the fungus Elsinoë euonymi-japonici, disfigures Japanese euonymus. Spots develop on both surfaces of leaves but are most common on the upper surface. The spots are very small, grayish white with a raised orange-cinnamon, waxy-appearing margin, and in the larger spots, a raised, dark center. When they are numerous, the spots may merge together. The centers of the leaf spots sometimes fall out. On the stems, spots are similar to those on the leaves, but they are often darker in color and more likely to merge together.
Prevention & Treatment: Rake up and destroy all fallen leaves and spray with thiophanate-methyl. See Table 1 for examples of products. Read and follow all directions on the label.
Several species of scale are pests on euonymus. Scales are unusual insects in appearance. They are small and immobile, with no visible legs. Scales vary in appearance depending on age, sex, and species. They feed on sap by piercing the leaf or stem with their mouthparts and sucking.
Numerous white male euonymus scales (Unaspis euonymi) may almost cover the undersides of leaves. The females are larger and darker.
Karen Russ, ©2009 HGIC, Clemson Extension
Euonymus Scale (Unaspis euonymi): This is the most common and most serious pest found on euonymus. The protective armor covering of an adult female euonymus scale is dark, oyster-shaped and about 1/16-inch in length. Adult males are very small, winged insects that leave their narrow, white armored covering for mating. The eggs laid by the female are yellow and found beneath the female’s covering. When the eggs hatch, the crawlers (immature forms) move around before forming their own protective covering. Males typically outnumber females. With a heavy infestation, clusters of white males can be easily seen on leaves and stems. Initial symptoms of euonymus scale infestation are yellow spots on leaves. With a heavy infestation, branches and possibly the entire plant may die.
Yellow spots on top surface of leaves are an early symptom of euonymus scale (Unaspis euonymi) infestation. Note scales along leaf veins.
Karen Russ, ©2009 HGIC, Clemson Extension
Prevention & Control: The following Euonymus species are resistant to euonymus scale: E. alatus ‘Compactus’ and E. fortunei ‘Acutus.’ Consider using these in new plantings. Euonymus scale is difficult to control. With light infestations, scale can be scraped off by hand and destroyed. Prune out and promptly dispose of heavily infested branches. Scales tend to thrive on stressed plants. Follow a recommended fertility program, mulch, and water plants weekly during drought to promote plant health.
Horticultural oils (also called supreme, superior or summer oils) work very well to control armored scales, such as the euonymus scale, on ornamentals by penetrating their waxy covers and smothering them. Horticultural oil sprays will kill the eggs, crawlers (immatures) and the adult scales. Horticultural oils applied at higher rates of 3% to 4% (7½ to 10 tablespoons oil per gallon water) during the dormant season (winter to early spring) will penetrate the thick waxy covers and kill the overwintering adults and eggs. Applications at lower rates of 2% (5 tablespoons oil per gallon water) can be used during the late spring (April) to target the crawlers and the newly settled scales with thin waxy covers. It is best to spray when temperatures are between 45 and 85 degrees and in the early evening due to plant sensitivity and to slow the drying time of the oil spray. More than one application may be necessary. See Table 1 for examples of products.
Adult scales are relatively protected from contact insecticides by their waxy covering, but their immature forms, called crawlers, are susceptible. However, contact insecticides will often kill the naturally occurring enemies of scale. Monitor the crawler emergence with sticky cards, double-faced tape wrapped around a branch, or by putting an infested shoot or leaf into a baggie and watching for crawler movement. Crawler activity often coincides with the flush of new plant growth in the spring. However, some scale species may have overlapping generations with an extended crawler emergence period, such as along the coast. These crawlers are often yellowish-orange, and appear as moving specks of dust.
If contact insecticides are necessary, the following are effective against crawlers: acephate, bifenthrin, cyhalothrin, malathion, and cyfluthrin. See Table 1 for examples of products. Make sure that crawlers are present before using these pesticides. Apply three sprays at 10-day intervals. As with all pesticides, read and follow all label instructions and precautions.
A soil application around the base of the infested plant with a product containing dinotefuran used once in the spring will help control armored scales. See Table 1 for examples of products. These may be found at landscaper supply stores. Read and follow all label instructions and precautions. Soil applications may be used in addition to sprays with horticultural oil. Note: Soil applied products containing imidacloprid do not effectively control armored scales, such as euonymus scale.
Table 1. Fungicide and Insecticide Products for Home Landscape Use.
|Active Ingredient||Examples of Products|
|Acephate||Bonide Systemic Insect Control Concentrate|
|Bifenthrin||Ferti-lome Broad Spectrum Insecticide Concentrate
Hi-Yield Bug Blaster Bifenthrin 2.4 Concentrate
Monterey Turf & Ornamental Insect Spray
|Cyfluthrin||Bayer Advanced Vegetable & Garden Insect Spray Concentrate|
|Cyhalothrin||Spectracide Triazicide for Lawns & Landscapes Concentrate; & RTS
Martin’s Cyonara Lawn & Garden Concentrate; + RTS
|Chlorothalonil||Bonide Fung-onil Concentrate
Ferti-lome Broad Spectrum Landscape & Garden Fungicide Concentrate
GardenTech Daconil Fungicide Concentrate
Hi-Yield Vegetable, Flower, Fruit & Ornamental Fungicide Concentrate
Ortho MAX Garden Disease Control Concentrate
Southern Ag Liquid Ornamental & Vegetable Fungicide Concentrate
Tiger Brand Daconil Concentrate
|Copper Fungicide||Bonide Copper Fungicide Spray or Dust
Bonide Liquid Copper Concentrate
Camelot Fungicide/ Bactericide Concentrate
Monterey Liqui-cop Fungicide Concentrate
Natural Guard Copper Soap Liquid Fungicide Concentrate
Southern Ag Liquid Copper Fungicide
|Dinotefuran||Valent Brand Safari 2G Insecticide (granules)
Valent Brand Safari 20SG Insecticide
Gordon’s Zylam Liquid Systemic Insecticide
Gordon’s Zylam 20SG Systemic Turf Insecticide
Ortho Tree & Shrub Insect Control Ready to Use Granules
|Horticultural Oil||Bonide All Seasons Spray Oil Concentrate
Ferti-lome Horticultural Oil Spray Concentrate
Southern Ag ParaFine Horticultural Oil Concentrate
Monterey Horticultural Oil Concentrate
Summit Year Round Spray Oil Concentrate
|Malathion||Gordon’s Malathion 50% Spray
Hi-Yield 55% Malathion Insect Spray
Martin’s Malathion 57% Concentrate
Ortho Max Malathion Insect Spray Concentrate
Spectracide Malathion Insect Spray Concentrate
Southern Ag Malathion 50% EC
Tiger Brand 55% Malathion
|Mancozeb||Bonide Mancozeb Flowable with Zinc Concentrate
Southern Ag Dithane M-45
|Myclobutanil||Spectracide Immunox Multi-purpose Fungicide Concentrate
Ferti-lome F-Stop Lawn & Garden Fungicide Concentrate
|Propiconazole||Banner Maxx Fungicide
Bonide Infuse Systemic Disease Control Concentrate
Ferti-lome Liquid Systemic Fungicide II Concentrate
|Sulfur||Bonide Sulfur Plant Fungicide
Hi-Yield Wettable Dusting Sulfur
Safer Brand Garden Fungicide Concentrate
Southern Ag Wettable or Dusting Sulfur
|Thiophanate Methyl||Cleary’s 3336-WP Turf & Ornamental Fungicide
Southern Ag Thiomyl Systemic Fungicide
Diseases of the Euonymus Shrub
Both bacterial and fungal diseases can affect euonymus shrubs. Over-watering and improper spacing may contribute to the development of fungal diseases and following good cultural practices can often prevent outbreaks. When plants begin to show signs of infection, you may need to use chemicals to fight the disease. Identifying the exact disease will help you determine the appropriate course of action.
Powdery mildew causes the growth of white or gray fungus on the upper sides of the leaves of infected euonymus shrubs. Leaves sometimes turn yellow and drop from the shrub. Severe infections may cause new leaves to curl. To prevent powdery mildew, plant euonymus in a sunny location and avoid watering the foliage. Provide plenty of room between plants to improve air circulation.
Spray shrubs with fungicides containing sulfur, thiophanate-methyl or myclobutanil to prevent outbreaks of the disease. Prune back and discard infected branches. Sterilize pruning shears with rubbing alcohol between each cut to prevent spreading the disease. If one fungicide is used repeatedly, powdery mildew may build up a resistance to it. Use different fungicides to prevent this resistance.
A soil-borne bacterium called Agrobacterium tumefaciens causes outbreaks of crown gall. Round, abnormal growths called galls form on the stems and roots of infected plants. Crown galls weaken euonymus shrubs and may cause branches to die. These growths inhibit the passage of water and nutrients through the plant. No cure is available, but shrubs with crown galls may survive for several years.
Cut back branches below the galls and sterilize your tool between cuttings. This bacteria survives in the soil for two to three years, so avoid planting other susceptible plants in the same area.
Cercospora Leaf Spot
Cercospora leaf spot causes brown spots to form on leaves. These spots may merge and cause the whole leaf to turn brown but this disease rarely leads to the death of an infected shrub. Clean up and discard of fallen leaves. Apply fungicides containing thiophanate-methyl according to the directions on the label.
Small brown spots form on the leaves and twigs of euonymus shrubs infected with anthracnose. This fungal disease begins during wet, cool weather and may cause significant defoliation. Spray shrubs with chlorothalonil or copper fungicides to prevent anthracnose. These fungicides will not control the disease once infection occurs. Clean up fallen foliage and prune back diseased branches.
The fungal disease scab causes small, grayish spots with orange edges on both leaves and stems. Large spots may contain a darker, raised center. Remove fallen leaves and discard of them away from the garden. Apply thiophanate-methyl to the shrub to control scab.