By: Mary H. Dyer, Credentialed Garden Writer
What is volutella blight on plants? Also known as leaf and stem blight, volutella blight is a destructive disease that affects pachysandra plants and boxwood shrubs. Read on to learn about treating volutella blight.
Initial symptoms, which appear in early spring, frequently resemble winter injury. Volutella blight symptoms begin with delayed emergence of new growth and patches of wilted, discolored, yellow, red or bronze leaves that gradually increase in size before turning black and falling from the plant.
Greenish-brown, water-soaked cankers girdle the stems, causing the plant to shrivel and wilt as the cankers turn dark black or brown. Pinkish fungal spores often appear during humid weather.
Prune damaged growth. Wipe cutting tools with bleach solution or rubbing alcohol between each cut to prevent spread of disease. Shake or rake the plant to remove infected leaves, then destroy the debris.
Although fungicide sprays won’t cure volutella blight, application of lime sulfur or copper sprays may help in case of severe infestations. Spray plants just before growth appears in spring, and then continue throughout the growing season as directed on the label. Plants may benefit from an additional volutella blight treatment in autumn to protect late summer growth.
Remove plants if the blight is overly severe. Replace them with more disease-resistant shrubs or ground covers.
To prevent volutella blight, keep plants healthy and minimize stress with regular trimming, which improves air circulation and increases penetration of sunlight. Trim plants during dry weather.
Water plants in the morning so the foliage has plenty of time to dry before temperatures drop later in the day, as volutella blight is more prevalent in wet, humid conditions. Avoid heavy mulch, which may keep the growing environment overly damp.
Treat insect infestations as they appear, and clean beds and rake plant debris in autumn.
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Steph is a certified Square Food Gardening Instructor who has been gardening for more than 10 years in Canada where the winters are long and cold, and the summers are unpredictable. She is a volunteer for her community's Incredible Edible project. In the past she created an educational gardening space for seniors and taught classes at a local community center where she created her own curriculum and activities. She participated in several local municipal garden days where she set up a booth to educate citizens about the joy of gardening.
I hate bugs. I really do. But worse than insect damage in the garden are the diseases such as bacterial blight, which bugs transmit to plants as they munch and crunch through leaves.
Diseases are a whole other foe from insects. You can’t see disease in the same way as you can a bug. They can creep up on you and decimate an entire crop like a wave.
It’s also possible to transmit diseases in your garden yourself by poor sanitation habits and carelessness without even realizing it.
Diseases can crop up at any time in a plant’s life cycle. Bacterial blight usually waits for an injury to a plant and then it attacks – and once it does, your plant could be toast.
Both of these disease-inducing fungi display easy to spot symptoms.
It is a good idea to check your plants on a regular basis and treat any affected areas as early as possible as box blight becomes increasingly difficult to deal with as time passes.
The symptoms displayed depend on which fungus your plants are infected with.
Cylindrocladium buxicola – in the early stages of the disease, the plants will have patchy areas of brown, withered leaves and, as it progresses, the affected areas will lose their leaves. Other signs of infection to look for are black-striped, or entirely blackened stems and a slender grey fungus on the underside of leaves.
Author: SB_Johnny, licenced under CC-BY-3.0
Volutella buxi – plants affected by this fungus will show areas of yellowed leaves, with pink spots underneath during the early stages. These leaves will also fall later on.
Early blight displays several telltale signs, with symptoms usually appearing after the first fruits appear on the tomato plants. Early blight will rear its head as small, brown lesions that look like bullseyes.
There will be dead plant matter in the center. The lesions will rapidly grow, with the surrounding plant tissue yellowing and then turning brown before the leaves die and fall off the plant altogether.
Early blight does not usually affect fruits directly, but indirectly, it can be devastating. Because the plant will have no more foliage to protect the fruits, the fruits are often damaged from direct sun exposure.
Whichever blight you had, the technique for controlling it is the same. Blights are caused by fungal spores that are always present in the environment. You cannot eliminate them from your garden soil.
What you can do is – Rotate your ‘crops’ each year, never growing the same family of crop, such as tomatoes, in the same spot. Move them to a different location. Use a 3-4 year rotation.
Mulch plants to keep soil from splashing on lower leaves during rain storms.
Work around plants when their leaves are dry (not when they are wet).
Water plants in early morning so that leaves have time to dry quickly in the sun. If possible water plants from below, avoiding the foliage.
Prune any diseased leaves from plants and destroy- do not leave diseased materials lying in the garden.
Fungicide may be used to prevent blight. The active ingredient is chlorothalinol. Use a product labeled for the plant you are protecting, and follow all label instructions. Once a blight has started, a fungicide can protect the plant parts that are not infected.
In fall, remove all plants and fruit. Remove weeds. Till under any remaining materials.
Here is an article about tomato blights, if you are interested in tomatoes- http://www.ppdl.purdue.edu/PPDL/expert/tomato-blight.html
If you are interested in sterilizing small quantities of soil for starting seeds in pots or flats- http://www.colostate.edu/Depts/CoopExt/4DMG/Soil/sterile.htm
Please update this question if you have more questions about this information. Thank you for using our service.
Both of these disease-inducing fungi display not hard to spot symptoms.
It’s prudent to check out the plants regularly and handle some affected areas as soon as you can as box blight gets increasingly hard to cope with as time goes by.
The symptoms depend on which fungus your plants are infected with.
Cylindrocladium buxicola – in the first phases of the illness, the plant life has patchy areas of brown color, withered leaves, and, as it progresses, the impacted areas will lose the leaves.
Some other infection symptoms to consider are black striped, or perhaps whole blackened stems, and a slender grey fungus on the un of foliage.
Cylindrocladium buxicola – Box blight, showing how the dead foliage appears on the plant
Authors: Matthew Shulman* and Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 02/03/2019
What is boxwood blight? Boxwood blight (also known as box blight and boxwood leaf drop) is a devastating disease of boxwood (Buxus spp.) that can cause leaf loss and eventual death of affected shrubs. Boxwood shrubs are commonly grown as hedges and as individual plants in home landscapes and public gardens. Boxwood blight can affect any type of boxwood (Buxus spp.) including European or common boxwood (Buxus sempervirens) Korean littleleaf boxwood (B. sinica var. insularis), and Japanese littleleaf boxwood (B. microphylla var. japonica). In addition, the disease has been reported on Japanese and Allegheny pachysandra (Pachysandra terminalis and Pachysandra procumbens respectively), two common groundcovers. Boxwood blight has been found in Europe and New Zealand, and was first confirmed in the U.S. in 2011. The disease was first detected in Wisconsin (in Kenosha County) in 2018.
Boxwood blight can cause severe leaf loss and eventual death of boxwood shrubs. (Photo courtesy of David Clement, University of Maryland Extension)
What does boxwood blight look like? Initially, brown spots appear on the leaves. The spots eventually enlarge and merge together. Infected leaves turn brown and fall off. Boxwood blight can cause total leaf loss on a shrub within days of the first onset of symptoms. Dark brown to black sunken areas can also form anywhere on the stems, leading to branch dieback Boxwood blight often kills plants shortly after all of the leaves drop. Damage from winter burn (see University of Wisconsin Garden Facts XHT1239, “Winter Burn”), dog urine and other diseases such as Volutella blight (see University of Wisconsin Garden Facts XHT1191, “Volutella Blight”) may look superficially similar to symptoms of boxwood blight.
Where does boxwood blight come from? Boxwood blight is caused by the fungus Calonectria pseudonaviculata (sometimes referred to as Cylindrocladium pseudonaviculatum or Cylindrocladium buxicola) which thrives in humid, warm conditions. The fungus is typically introduced into any area on nursery plants that are infected, but not showing symptoms. Holiday wreaths containing boxwood sprigs have also been documented as a source of the boxwood blight fungus. Once the fungus has been introduced into the landscape, spores can be easily spread by splashing water (e.g., rain or sprinklers), wind or contaminated gardening tools (e.g., pruners, shovels, gloves). The boxwood blight fungus can survive and produce spores in dead boxwood leaves and branches (including those that have fallen onto the ground) for several years.
How can I save a plant with boxwood blight? Because boxwood blight is new to Wisconsin and relatively rare, eradicating the causal fungus may be possible. Therefore, if you find boxwood blight, remove and destroy any affected shrubs. Currently, free testing for boxwood blight is available through the UW-Madison Division of Extension Plant Disease Diagnostics Clinic (https://pddc.wisc.edu/). Plants (roots and all) confirmed to have boxwood blight, as well as any leaves or branches that have fallen from these plants, should be removed and destroyed by burning, deep burying (at least two feet deep) or double bagging (in plastic garbage bags), then landfilling. DO NOT compost any parts of infected shrubs. Thoroughly decontaminate any tools used in the removal process by dipping them for at least 30 seconds in 70% alcohol (e.g., rubbing alcohol) or (as a last resort) in 10% bleach. Spray disinfectants that contain at least 70% alcohol also can be used. Spray tools until they drip and then allow them to air dry.
How can I avoid problems with boxwood blight in the future? Consider using shrubs other than boxwood in your landscape. If you decide to use boxwood, choose boxwood blight resistant varieties where possible. In Wisconsin, hybrid boxwood ‘Green Gem’, common boxwood variety ‘Katerberg’ North Star®, and Korean littleleaf boxwood varieties ‘Eseles’ Wedding Ring®, ‘Franklin’s Gem’, ‘Winter Gem’ and ‘Wintergreen’ are hardy (to USDA hardiness zone 5) and have been documented to be resistant to box blight. Always buy boxwood shrubs from local reputable suppliers who have thoroughly inspected boxwood plants for evidence of boxwood blight. Isolate new boxwood shrubs from established boxwoods for several weeks before planting, as
boxwood blight symptoms not become apparent until weeks after purchase. DO NOT plant boxwoods in areas where boxwood blight has been a problem in the past, as the fungus can survive in boxwood debris (e.g., leaves and branches) for several years. When planting, space boxwood plants far enough apart from each other, as well as other shrubs, so that branches on adjacent shrubs do not overlap. This will increase air flow between plants and promote a drier environment that will be less favorable for boxwood blight. Avoid watering plants with sprinklers or overhead with hoses instead use a soaker or drip hose. This will limit splash of spores from plant to plant and also promote a drier environment that is less favorable for disease.
Leaf spots typical of boxwood blight on boxwood sprigs in a holiday wreath. (Photo courtesy Purdue PPDL)
Be cautious when buying holiday wreaths or other garlands. Avoid holiday decorations that contain boxwood, whenever possible. If you are unsure whether a wreath that you have purchased contains boxwood, assume that it does and dispose of it appropriately by burning, deep burying or double bagging and landfilling as described above. Be careful to collect and dispose of any leaves or branches that may have fallen from wreaths as well. Make sure that no potentially contaminated materials end up near boxwood shrubs in your yard. Under NO circumstances should you attempt to compost any suspected boxwood materials.
Once boxwood blight has been reported near your location, you may want to consider using preventative fungicide treatments for management. Fungicides containing chlorothalonil (alone or in combination with thiophanate-methyl or tebuconazole), fludioxonil, metconazole, and tebuconazole (as a stand-alone product) have been shown to provide good control of boxwood blight if applied prior to the development of any symptoms. These fungicides will not cure existing disease. If you decide to use fungicides, you will need to treat every seven to 14 days throughout the growing season. DO NOT use fludioxonil, metconazole, or tebuconazole as the sole active ingredient for all treatments. If you decide to use one of these active ingredients, alternate its use with at least one of the other active ingredients listed above (except DO NOT alternate metconazole and tebuconazole as these products are chemically related). Alternating active ingredients will help minimize problems with fungicide-resistant strains of the boxwood blight fungus. Be sure to read and follow all label instructions of the fungicide(s) that you select to ensure that you use the product(s) in the safest and most effective manner possible.
Finally, routinely (e.g., weekly) check boxwood plants for boxwood blight. Immediately remove any symptomatic plants and fallen leaves and branches, and dispose of them as described above.
For more information on boxwood blight: Contact your county Extension agent.
Boxwood leafminer larva feeding inside leaf.
Clemson University – USDA Cooperative Extension Slide Series, Bugwood.org
Boxwood Leafminer (Monarthropalpus flavus): This is the most serious insect pest that attacks boxwood. The leafminer is the larva (immature form) of a small, orangish mosquito-like fly. These flies are less than ⅛-inch long and can often be seen swarming around boxwoods in the spring. The adult female fly inserts eggs with her ovipositor (egg laying structure) into new boxwood leaves through the leaf’s upper surface. When the larvae hatch, they feed inside the leaf, creating a mine. Larvae are orange and about ⅛-inch in length. They overwinter (survive the winter) inside the leaves. Adults emerge from the leaves the following spring, just after new growth occurs on boxwoods. There is one generation per year. American boxwood is the preferred host plant, but English and Japanese boxwoods (B. microphylla var. japonica) are also susceptible.
Boxwood leafminer attacks result in irregularly shaped swellings on the leaf. There may be a slightly blistered appearance on the leaf’s undersurface. Blistering may not be obvious until late summer. Infested leaves typically turn yellow or brown in splotches, are smaller, and drop sooner than healthy leaves. A heavy infestation can cause serious loss of leaves and result in the death of the boxwood.
Prevention & Control: Use of insecticides against boxwood leafminer is not recommended unless damage is intolerable. Insecticides are most effective against this pest when adults have emerged and before they can lay eggs. Adults typically emerge over a three-week period but live only a few days
Distorted, splotchy leaves afflicted with boxwood leaf miners.
John A. Weidhass, Virginia Polytechnic Institute and State University, Bugwood.org
Contact insecticides that are effective against boxwood leafminer adults and are labeled for homeowner use include malathion. With these insecticides, begin treatment in mid-April to early May when the adult flies are seen hovering around the boxwood plants. Foliar systemic insecticides, such as sprays with acephate or spinosad, are effective when leafminers are present in mines. Soil treatments with dinotefuran or imidacloprid will control leafminers, but may take two weeks or more to begin providing season-long control. Dinotefuran may move into shrubs more quickly than imidacloprid for faster control. See Table 1 for examples of products. As with all pesticides, read and follow all label instructions and precautions.
Boxwood Mite (Eurytetranychus buxi): The boxwood mite or boxwood spidermite is not an insect but is more closely related to spiders. The adult is green to yellowish-brown in color, has eight legs, and is tiny, about 1 /64-inch long. Since mites are so small and early symptoms are not distinctive, it is easy to overlook the problem until a heavy infestation occurs and greater damage has occurred. This pest overwinters as eggs on the underside of leaves, and the eggs hatch in the spring. Boxwood mites develop and breed rapidly, resulting in eight or more generations per year.
All stages of boxwood mite feed on both leaf surfaces. They pierce the leaf to suck out plant sap. During feeding, they inject toxic saliva, which results in stippling (tiny, yellow scratch-like spots) forming on the leaf’s upper surface. Boxwood mites prefer feeding on young leaves, but the damage is most obvious on second-and third-year leaves. From a short distance, the infested boxwood appears unhealthy with a dingy silvery color.
Prevention & Control: Naturally occurring enemies of mites include various predatory mites, ladybird beetles (ladybugs), and other insects. These predators will usually suppress mite populations. Since insecticide use kills predators as well as mites, insecticides should be avoided unless absolutely necessary.
To determine whether insecticide use is needed, it helps to know how many mites are present. Hold a white sheet of paper under a branch and strike the branch. The mites that are knocked off will be seen crawling around on the paper. If more than 15 mites are seen per whack, serious damage can result.
Mites can be removed with a strong spray of water if applied on a regular basis. Horticultural oil applied at the summer rate of 1 – 2% (2-1/2 to 5 tablespoons oil per gallon of water) will kill eggs and adult mites. Horticultural oil may be sprayed when temperatures are between 45 and 85 degrees. Insecticidal soaps can also provide control when applied before population numbers get too high. Miticides labeled for homeowner use against boxwood mites include tau-fluvalinate. These products should be applied when mites are present and again in seven to 10 days. See Table 1 for examples of products. As with all pesticides, read and follow all label instructions and precautions.
Boxwood Psyllid (Psylla buxi): The adult is a small, greenish insect, about ⅛-inch long. It has clear wings and strong legs adapted for jumping. It looks like a tiny cicada that hops or flies away when disturbed. Both the adult and nymph (the immature insect stage which resembles the adult) feed by piercing leaf surfaces and sucking plant sap.
Boxwood psyllid feeding causes cupped, stunted leaves.
Daniel Herms, Ohio State University, Bugwood.org
Nymphs hatch from eggs in the spring. They produce a white, waxy material that often covers their bodies. Nymphs feed on buds and young leaves. This feeding results in the typical cupping of leaves and stunted twig growth that are seen with this pest. Plants tend to outgrow the injury by midsummer.
After further development during the spring, adults are formed. Adults also feed on boxwood, but are less damaging than the nymphs. Adult females lay eggs under bud scales. The immature nymphs develop within the eggs, where they remain until spring. They emerge in spring to feed and complete development to adults. Only one generation occurs per year.
Prevention & Control: Insecticides should only be used if infestations are heavy. Acephate is a foliar systemic insecticide, and sprays will control boxwood psyllids. Soil treatments with dinotefuran or imidacloprid will control psyllids, but may take two weeks or more to begin providing season-long control. Dinotefuran may move into shrubs more quickly than imidacloprid for faster control. See Table 1 for examples of products. As with all pesticides, read and follow all label instructions and precautions.
Table 1. Insecticides & Fungicides for Boxwood Diseases & Insect Pests
|Insecticides & Fungicides||Examples of Brand Names & Products|
|Acephate||Bonide Systemic Insect Control Concentrate|
|Chlorothalonil||Bonide Fung-onil Multi-purpose Fungicide Concentrate |
GardenTech Daconil Fungicide Concentrate
Ferti-lome Broad Spectrum Landscape & Garden Fungicide Conc.
Hi-Yield Vegetable, Flower, Fruit & Ornamental Fungicide
Ortho MAX Garden Disease Control Conc.
Southern Ag Liquid Ornamental & Vegetable Fungicide
Tiger Brand Daconil
|Copper-based Fungicides||Bonide Liquid Copper Concentrate |
Bonide Copper Fungicide Wettable Powder
Camelot O Fungicide/ Bactericide Concentrate
Monterey Liqui-Cop Fungicide Concentrate
Natural Guard Copper Soap Liquid Fungicide Concentrate
Southern Ag Liquid Copper Fungicide
|Dinotefuran||Gordon’s Zylam Liquid Systemic Insecticide (10% concentrate) |
Ortho Trees & Shrub Insect Control Granules (2%)
Valent Brand Safari 20SG Insecticide (20% concentrate)
Valent Brand Safari 2G Insecticide (2% granules)
|Horticultural Oil||Bonide All Seasons Spray Oil Concentrate & RTS 1 |
Ferti-lome Horticultural Oil Spray Concentrate & RTS 1
Monterey Horticultural Oil Concentrate & RTS 1
Safer Brand Horticultural & Dormant Spray Oil Concentrate
Southern Ag ParaFine Horticultural Oil
Summit Year Round Spray Oil Concentrate
|Imidacloprid||Bayer BioAdvanced Garden 12 Month Tree & Shrub Insect |
Control Landscape Formula
Bonide Annual Tree & Shrub Insect Control with Systemaxx
Ferti-lome Tree & Shrub Systemic Insect Drench
Hi-Yield Systemic Insect Spray Concentrate (drench)
Martin’s Dominion Tree & Shrub Insecticide
Monterey Once A Year Insect Control II
|Insecticidal Soap||Natural Guard Insecticidal Soap Concentrate |
Safer Brand Insect Killing Soap Concentrate
|Malathion||Bonide Malathion 50% Insect Control |
Gordon’s Malathion 50% Spray Concentrate
Hi-Yield 55% Malathion Insect Spray
Martin’s Malathion 57% Concentrate
Ortho Max Malathion Insect Spray Concentrate
Southern Ag Malathion 50% EC
Spectracide Malathion Insect Spray Concentrate
Tiger Brand 50% Malathion Spray
|Spinosad||Bonide Colorado Potato Beetle Beater Concentrate |
Bonide Captain Jack’s Deadbug Brew Concentrate & RTS 1
Conserve SC Turf & Ornamental Concentrate
Ferti-lome Borer, Bagworm & Leafminer Spray Concentrate
Monterey Garden Insect Spray Concentrate
Natural Guard Spinosad Bagworm, Tent Caterpillar & Chewing
Insect Control Concentrate & RTS 1
Ortho Insect Killer Tree & Shrub Concentrate
Southern Ag Conserve Naturalyte Insect Control Concentrate
|Tau-Fluvalinate||Bayer BioAdvanced 3-in-1 Insect, Disease & Mite Control Conc. & RTS 1 |
Bayer BioAdvanced 3-in-1 Insect, Disease & Mite Control I Conc. & RTS 1
|Thiophanate methyl||Cleary’s 3336-WP Turf & Ornamental Fungicide |
Southern Ag Thiomyl Systemic Fungicide
|1 RTS = Ready to Spray (a hose-end spray bottle)|
If this document didn’t answer your questions, please contact HGIC at [email protected] or 1-888-656-9988.
Marjan Kluepfel, Former HGIC Horticulture Information Specialist, Clemson University
Janet McLeod Scott, Former Horticulture Information Specialist, Clemson University
James H. Blake, EdD, Extension Associate/Adjunct Professor, Dept. of Plant and Environmental Sciences, Clemson University
Clyde S. Gorsuch, PhD, Emeritus Faculty, Entomology, Clemson University
Steve N. Jeffers, PhD, Dept. of Entomology, Soil & Plant Science, Clemson University
Joey Williamson, PhD, HGIC Horticulture Extension Agent, Clemson University
This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.