Butterfly Bush Diseases – Treating Diseases Of Butterfly Bush

Butterfly Bush Diseases – Treating Diseases Of Butterfly Bush

By: Liz Baessler

Butterfly bush, also called buddleia or buddleja, is a relatively trouble free plant to have in the garden. It grows so easily that in some places it’s considered a weed, and it is affected by very few diseases. Keep reading to learn more about butterfly bush disease problems and how to go about troubleshooting butterfly bush issues.

Butterfly Bush Diseases

Downy mildew is a relatively common problem that can occur when temperatures are cool and the plant’s leaves are wet for a long period of time. It looks just like the name suggests, with furry patches of mildew appearing on the undersides of leaves. The opposite sides of the leaves don’t grow mildew, but they may turn yellow or brown, and the whole leaf may become misshapen.

The best way to prevent it is to keep the bushes far apart for airflow and to keep the ground around them clear of leaves. If you already have mildew, remove any really infested plants or branches and spray with fungicide.

Another one of the common butterfly bush diseases is rhizoctonia, a fungal root rot that makes leaves yellow and drop and destroys the roots. It’s hard to totally wipe out rhizoctonia, but applying fungicide to the soil can help.

One more of the buddleia diseases is phytophthora, another fungal root rot. It’s noticeable above ground by yellowing leaves, smaller than usual flowers, and stems rotting on the plant. Underground, the outer layers of the roots rot away. Phytophthora can sometimes be treated by the application of fungicide, though sometimes even with treatment the plant will die.

Treating diseases of butterfly bush is more a means of prevention than anything else. Typically, if grown in suitable locations with well-draining soil and plenty of air circulation, most issues with these shrubs can be alleviated right from the get-go.

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How to Grow Butterfly Bushes Responsibly

To plant or not to plant has been the question surrounding butterfly bush (Buddleia or Buddleja davidii) for years. Its many blossoms, although irresistible to butterflies, can lead to aggressive re-seeding. Thankfully, breeders have been able to develop sterile or nearly-sterile cultivars, often referred to as summer lilac, and those are the ones we will focus on here.

Points to Consider Before Introducing Butterfly Bush

As mentioned above, they appear in invasive plant lists in many states of US, so check with the authorities before picking any variety. The seedless or sterile types like ‘Miss Ruby’, ‘Asian Moon’, and ‘Blue Chip’ are often preferred for this reason.

Another thing worth knowing is that despite their name, they are not beneficial to butterflies in any way apart from offering their sweet nectar. None of the butterfly bushes serve even as a secondary host plant for any caterpillar.

Despite being perennials, most cultivars die in winter, especially in the Northern regions, with the roots growing fresh stems again the next season. So, they are not suitable if you want a low-maintenance evergreen garden.

The butterfly bush (Buddleia davidii) is a beautiful, fast-growing, deciduous shrub with masses of blossoms—long, spiked trusses—that bloom from summer to autumn.

Its flowers come in many colors, though butterflies seem to prefer the lavender-pink (mauve) of the species to the white and dark purple cultivars.

Also called “summer lilacs,” butterfly bushes are hardy to Zone 5 and remain evergreen from Zone 8 south. The shrub is low-maintenance, only requiring dead-heading and annual pruning in later winter to encourage flowers and a compact shape.

Invasive Concerns

Please note that the butterfly bush, originally imported from China, has been classified as an invasive species in most U.S. regions. In other words, the butterfly bush is known to crowd out native plants that are essential to wildlife, including butterflies and birds. In warm climates, it can become a noxious weed and spread aggressively, while in cooler climates, it mostly stays contained within a garden’s cultivated soil if gardeners deadhead the flowers.

Despite the “butterfly” name, keep in mind that this shrub is not a “host plant” for butterflies in that it does not support butterfly reproduction and lifecycle. Caterpillars do not feed on butterfly bushes rather, it only provides nectar to adult butterflies. If you do have a butterfly bush, be sure to add native host plants such as milkweed, aster, and dill if you want the butterflies to stay. See plants that attract butterflies.

If you would still like to put a butterfly bush in your garden, there are a few species of non-invasive butterfly bushes native to the southwestern US . Please check with your local cooperative extension for more information.

How to keep butterfly bush from spreading noxiously

AURORA - Butterfly bush, also known as summer lilac, Buddleia or Buddleja, is a very popular garden plant in the Pacific Northwest and other temperate regions of the world. Photos of its beautiful blossoms grace the pages of slick gardening magazines and catalogs, television programs and garden center displays. Garden writers laud the butterfly bush as a fast-growing, robust, easy-to-grow shrub that attracts a wide variety of butterflies.

But there's a dark side to this popular plant. Butterfly bush can be a very aggressive, or invasive non-native shrub that, in certain situations, can overtake native vegetation, according to horticulturists with the Oregon State University Extension Service and weed biologists with Oregon's Department of Agriculture (ODA).

In Oregon, the ODA officially classified it as a class "B" noxious weed in 2004. Its strategic plan includes efforts to eradicate butterfly bush in the wild, but not from people's yards.

James Altland, nursery crops researcher at OSU's North Willamette Research and Extension Center in Aurora, and his student Julie Ream, are studying the relative invasiveness of cultivated species of butterfly bush in Oregon.

Butterfly bush is extremely invasive in natural areas. There are serious infestations on the North Fork of the Willamette River near Oakridge and along the Coquille River near the coast. It has spread to most of the counties in western Oregon and Washington. It has been a huge problem in England, where it is one of the top 20 weeds, having overtaken large tracts of disturbed land 50 years after it was introduced from China. It is a terrible problem in New Zealand as well, especially in areas prone to frequent flooding.

"We want to know if there are types of Buddleia that can be grown safely without escaping and threatening the natural environment," said Altland.

In reviewing the scientific literature about the invasiveness of butterfly bush in the United Kingdom, the OSU researchers found that seed there requires a long time to develop and release from the plant. British researchers have discovered that flower heads from a previous summer do not release seed until dry weather occurs the following spring, said Altland. Practically applied, this means that if nurseries and home gardeners prune all the spent blossoms off their butterfly bushes in the fall, it is a way of controlling the release of seed from the plant.

Altland and Ream are conducting trials on five cultivars of butterfly bush commonly produced in Oregon to see exactly when seeds are released in the Willamette Valley, as seed releases may be slightly different from England. They also conducted research on the soils, and habitat of butterfly bush-infested sites to determine and describe what factors favor these infestations in Oregon.

So far, they have found butterfly bush infestations in a wide variety of sites, from floodplains to mountain slopes, said Altland. They found the densest infestations in burned sites in reforestation areas and in frequently disturbed floodplains and riparian areas. They found few escaped seedlings from nurseries, as production nurseries often cut back plants at the end of the year to encourage branching.

Both OSU and ODA scientists are encouraging home gardeners to pay close attention to choosing butterfly bushes that are cultivated varieties, not the straight wild species Buddleia davidii. Only this species Buddleia davidii, not specially bred cultivars are subject to Oregon's noxious weed listing. It is most commonly seen growing wild along roadsides, in riparian areas and in forest openings.

Some cultivars have been found to produce much less seed than others. For example, a study at Longwood Gardens in southern Pennsylvania found large differences in the amount of viable seed produced by B. davidii varieties. For example, cultivars 'Summer Rose' and 'Orchid Beauty' produced 20 times fewer viable seeds than 'Potter's Purple' and 'Border Beauty'. The study also found that a single flower cluster of 'Potter's Purple' was found to produce more than 40,000 seeds. In the Longwood study, some Buddleia species and hybrids produced fewer viable seeds than B. davidii and likely have lower potential for escaping gardens and colonizing natural areas.

Altland would like to conduct similar studies in Oregon.

If you already have butterfly bush on your property or are planning on planting some soon, there are ways to keep it in control.

Don't let Buddleia go to seed. Deadhead, or clip off all flower heads in the fall. Do not wait until spring.

Do not leave the clippings on the ground, as they can easily take root and create a new plant. Dispose of plants by sending away in your yard debris pickup service, where it will be ground up and composted. Or burn the branches. Whatever you do, don't dump the clippings along a roadside or along a creek or river, as these are preferred habitats for escaped butterfly bush.

Watch your property for new seedlings. Dig up and get rid of any volunteer bushes. Don't give them away to friends.

Buddleia or Buddleja are both considered correct spellings of the Latin name of the genus of the butterfly bush, according to the gardeners' encyclopedia of ornamental plants called Flora: A Gardeners Encyclopedia, published by Timber Press. The genus has about 100 species in the wild. Most grown in our region are native to Asia. Others originate from South Africa. And some are from South America. Only a few species in the genus are domesticated and garden-grown in our region.

In addition to ODA's "B" noxious weed listing, Buddleja davidii appears on the "Most Invasive" species list of the Pacific Northwest Exotic Pest Plant Council and the Native Plant Societies of Oregon and Washington. The OSU Extension Service Master Gardener Program no longer recommends it for butterfly gardens because of its invasiveness.

Treating a Butterfly Bush for Pests

Plant a flowering butterfly bush (Buddleia davidii) in your garden to attract lively and colorful butterflies. There are about 100 varieties of these bushes, many of them shrubs. These plants usually grow up to a height of 8 to 14 feet and have a spread circumference of 3 to 15 feet. The leaves of butterfly bushes are long, lance-shaped (wide at the central portion) and grayish-green in color. The flowers bloom in various shades of orange, white, lilac, purple, pink and lavender from June to July. This bush needs moist, loamy and well-drained soil along with full sun or light shade.

Pests that Attack Butterfly Bushes

Butterfly bushes are one of the excellent choices for welcoming butterflies to the garden. This plant is easy to maintain and it can even tolerate urban pollution. In general, the butterfly bush is rarely attacked by pests or plant diseases.

Even though the butterfly bush has good resistance against pests and diseases, some predators such as wasps, spiders, birds, ants, aphids and flies can threaten it. Japanese beetles, spider mites and a species known as the checkerspot butterfly are also known to attack this plant. Most of the pests can be controlled by the proper and effective use of pesticides.


Treat an infestation of aphids with insecticidal soaps, summer oils and insecticides such as chlorpyrifos, acephate and Malathion. You may need to do follow-up application in the case of oils and soaps. Acephate can effectively kill the aphids that hide below the curling leaves as it shows systemic activity.

Spray acephate directly on the plants after removing the old growth. A single application can work wonders.

Checker Spot Butterflies, Mites and Oleander Scale

Destroycheckerspot butterflies with pesticides containing Bacillus thuringiensis var. kurstaki. Treat mites and oleander scale (Aspidiotus nerii) by applying Ultra-Fine® pesticide oil.


Control the attack of genista caterpillars by spraying water or a solution of water and mild dishwashing detergent directly on the plant.

Importance of Regular Pruning

Butterfly bushes are low-maintenance plants. However, regular pruning is important for healthy blooms and also for removing the dead and damaged wood, which may attract harmful pests. If pests attack, immediately remove the infected branches and use an appropriate insecticide. New shoots will probably appear in a few days and the plants survive.

Butterfly bushes also attract bees and hummingbirds to the garden, thus making it more colorful. The plant bears flowers in long clusters, and it is a well-known garden plant because of its vibrant color flowers, fragrance and notable resistance against insects and diseases.

Butterfly Bush Care

Give butterfly bush about an inch of water a week while they're actively growing, if rain isn't sufficient, but don't worry if you occasionally forget to irrigate. In the first year after planting, these bushes need regular water to develop strong roots. After they're established these plants are relatively drought-tolerant. Fertilizing isn't usually necessary, as it encourages foliage at the expense of flowers.

You can prune your bushes anytime, and you will probably need to prune a few times each summer to keep them under control. Keep faded flowers deadheaded to encourage more blooms.

Mulch the plants generously to protect them during the winter. Many gardeners prune their butterfly bushes all the way to the ground in late winter. This dormant-season pruning allows extra root and evergy reserves to quickly heal the wounds and supports vigorous spring growth. When the bushes break dormancy in the spring, give them some compost and fresh mulch. If you didn't prune during the winter, it's okay to prune just before a flush of new growth appears.

Buddleia are seldom bothered by pests or disease, although mullein moths, caterpillars and spider mites can attack them, and the plants are occasionally plagued by fungal infections. If you see insects, try knocking them off with a strong blast of water from the hose, or spray the bushes with insecticidal soap. But try to avoid using pesticides, as they also kill visiting butterflies, bees and other beneficial garden creatures.

To control fungus problems, which can flourish on wet leaves, water bushes early in the day, and use a soaker hose or drip irrigation when possible. Remove diseased plant parts and discard them — but not in your compost pile, where diseases can spread.

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