Hosta Plant Diseases and Treatments – Tips On Treating Hosta Diseases

Hosta Plant Diseases and Treatments – Tips On Treating Hosta Diseases

By: Mary H. Dyer, Credentialed Garden Writer

Hostas have becomes garden favorites in recent years, and it isn’t difficult to figure out why. Available in a huge variety of sizes, colors and forms, hostas provide color and interest in those difficult, shady garden spots. Hostas are relatively trouble free, but they can be affected by various diseases. Read on to learn more about a few of the most common hosta plant diseases and treatments.

Common Hosta Diseases

Diseases of hosta plants generally include both fungal and viral issues, as well as problem caused by nematodes in the soil.

Fungal Diseases

Anthracnose – This disease plagues not only hosta, but many other types of plants, including trees and tomatoes. Although it usually isn’t fatal, the large, pale brown spots, small black splotches and a tattered appearance can definitely detract from the appearance of the plant. A fungicide may help prevent the disease. Be sure hostas are spaced widely enough to provide air circulation; anthracnose thrives in damp conditions.

Fusarium root/crown rot – This fungal disease usually appears in late spring, when leaves turn yellow and brown before they die and drop from the plant. Stems near the soil line often display a dry, brown or black decay. Infected plants should be removed, as plants with crown rot normally cannot be treated.

Sooty mold – Common hosta diseases include sooty mold, which is often found on hostas planted under trees affected with sap-sucking pests, such as scale or aphids. The pests produce a sugary excrement, which drops on the plant and attracts the dark, unattractive mold. Sooty mold is unsightly but usually harmless. However, it can block light, which can affect the health of the plant. The fix? Wash the guck off with warm, soapy water and treat the plant for pests.

Viral Diseases

Hosta virus X – Early symptoms of hosta virus X include green or blue spots that give the leaves a mottled appearance. The symptoms look normal at first, but the leaves may become twisted, puckered or distorted as the disease progresses. Unfortunately, there is no cure for this viral disease, which is easily spread from plant to plant on garden tools or hands. Plants should be destroyed as soon as possible. Treating hosta diseases such as Hosta virus X requires cleaning and sanitizing of all garden tools.

Other viral diseases include tomato ringspot, tomato wilt, impatiens necrotic spot and Arabis mosaic. Although symptoms vary, affected plant leaves tend to display puckering and yellowing. Some may develop concentric rings that look like targets.

Nematodes

Nematodes are miniscule worms that live in the soil or inside the tender hosta leaves. The foliage turns yellow when the nematodes are feeding in early summer. As the season progresses, the leaves develop brownish streaks between the veins. Eventually, entire leaves turn brown and drop from the plant. Affected leaves should be destroyed. To prevent the nematodes from spreading, water the plant at the soil level to keep the leaves dry.

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Hosta Plant History – Learn About The Origin Of Hosta Plants

When it comes to favored plants, hosta is fairly new on the horizon for North American gardeners. However, in the last couple of decades, its popularity has exploded and hosta has become the go-to plant for shady, hard-to-plant spots in the landscape. In fact, hostas have become the number one perennial sold in the United States. But what about the origin of hosta plants? And how did they make their way into our gardens?


Diseases Of Hosta Plants: Learn About Hosta Plant Problems And Treatment - garden

TheGardenLady received this question from Pete (You can see images of his hostas above):

I have many green hosta plants that for the last couple years have wilted leaves or are otherwise distorted.The plants are quite old but were always healthy till now. Any ideas?

Though hostas are known to have few pest and disease problems, sadly they do develop some diseases and do get some pests. Some of these
problems may not kill the plant but makes them look unattractive. I have a feeling that your problem is not a killer.

You do not say where you live, but in many areas of the US, this spring has had a lot of rain. Some diseases need the excess moisture
to cause problems. This excess moisture on the plants is either through excessive rain or excessive overhead watering.

Because your plants have always been healthy in the past, my suspicion is that your plants have developed a fungi. I believe it is a fungi because you say the problem is only on the leaves. I hope you have examined the roots of your hostas and found that they are not rotted. But without actually seeing the plant, I will not make a diagnosis. Here is an excellent website that shows photos of hosta diseases and gives descriptions of the problems.

But before you make the decision about what your hosta problem is, I suggest cutting off a big section of the diseased leaf (and root if that has a problem) and putting the diseased plant parts in a ziplock bag and taking it to your local agricultural extension office or Master Gardener Office. They will identify the problem accurately and tell you how to treat your problem- plus they will tell you if you should spray a fungicide and how to use any chemicals if they recommend them.

If you have a fungus you can cut away any damaged leaves. Put these cut leaves in your garbage- do NOT compost any leaves with a fungus.

And you will have to disinfect any gardening tools used in your hosta beds. You do not want to spread any diseases by using tools that touched your unhealthy plants. Those scissors you cut your leaves with should also be disinfected. Two of the common household products you can use to disinfect tools are bleach or Lysol. Here are instructions on how to disinfect your tools.


Diseases Of Hosta Plants: Learn About Hosta Plant Problems And Treatment - garden

Fortunately, there only a handful of fungal diseases that affect hostas. With the possible exception of Southern Blight, they are very rare in the home landscape.

Fungal diseases are by far the most common type of disease of landscape plants. The one thing they all have in common is the need for moisture in order to thrive, grow and reproduce. If the leaf or soil around the roots is kept relatively dry, the potential for fungal diseases will be limited.

Fungicides commonly used in the home landscape are preventative. This means that they must be in place before the fungal spores land. So, before even thinking about using a fungicide on your hostas, be sure to have a proper diagnosis from a university or other plant diagnostic laboratory.

Southern blight of hosta also called white mold, petiole roty and crown rot is caused by the fungus Sclerotium rolfsii. In addition to hosta it is also an infection daylily, astilbe , peony, phlox , ajuga , delphinium and potato.

The disease commonly attacks the plant at or just below the soil line. The first symptom is a yellowing and wilting of the foliage. The fungus produces a large amount of cottony white, thread like material called mycelium, which can grow up the stems of plants and also spread out across the soil to infect other plants.

Although this is called Southern blight, it does occur in northern gardens too but is fairly uncommon. It is a difficult disease to control and, for the home hosta gardener, the key is sanitation. If you have this disease (diagnosed by a reputable plant lab), be especially careful in moving plants around the garden and transporting soil from one location to another on tools.

In Southern states, the process of solarization my kill the fungus in the soil. This involves covering the area with clear plastic sheets and letting the sun "cook" the soil. Unfortunately, this does not seem to work as well in northern areas.

If you have a serious problem that cannot be controlled by sanitation or solarization, you might need to hire a commercial pesticide applicator. Only they have access to the soil sterilants that are supposed to be effective on this disease. They are not available to the home grower.

Here is a great publication by Iowa State University on this subject.

Fusarium is a common fungal root rot organism that affects a wide variety of plants in the landscape and vegetable garden. It has been reported on hostas primarily in plant nurseries in the Southeast United States but rarely in home landscapes.

Since it attacks the roots of the plant, it ultimately leads to severe wilting and death of the plant. The crown may be covered with brown pockets and the roots will be brown or black instead of whitish as healthy roots appear. In less severe cases, the plant may be stunted, have low vigor and does not emerge well in the spring.

This is a soil borne fungus so, IF you have hostas that are diagnosed by a university or other plant laboratory, you should not replace the plant with others that are susceptible to it.

This is a fungal leaf disease that is common to many types of plants in the landscape or garden from oak and maple trees to tomatoes. It is generally a disease of the early spring especially during cool, wet weather. Fortunately, it is not a fatal disease but does cause the plant to loose some vigor and may degrade the aesthetic value of the hosta.

Do not assume that brown or black blotches on the hosta leaves are anthracnose. Be sure to have it properly diagnosed at a university or other plant laboratory. IF it is anthracnose, they will prescribe possible treatment alternatives.


Signs and symptoms of hosta petiole and crown rot

Symptoms of the disease include marginal yellowing and browning of the leaves, beginning with the lower leaves. As the disease progresses, the leaves discolor entirely and wilt. In the final stages of the disease, most of the leaves completely collapse and lay flat on the ground. Because the bases of the petioles are rotted, the leaves can be easily pulled away from the crown of the plant.

A closer look at the devastation reveals a white mat of fungus fanning out from the infected crown across the soil surface. Look a bit closer and you can see thousands of tiny, spherical sclerotia in the rotted crown. Sclerotia of S. rolfsii are somewhere between BB's and pepper grounds in size and vary in color from white (newly developed) to brick red. Sclerotia, the survival pod of the fungus, allow it to hang on patiently in hostile environments, then wake up and attack when a likely victim (hosta and many other plants) appears.


Recommended Hostas

The following is a partial list of hostas that should do well in the Georgia landscape:

H. "Antioch" has leaves of light gray-green with a creamy white border. Mature clumps of the 8 to 12 inch-long tapered leaves measure 18 inches tall and 30 to 36 inches across. "Antioch" emerges later in spring than most hostas, avoiding damage by late frosts. It is striking as a specimen plant, in large containers and when massed.

H. "August Moon" is a desirable gold hosta for all-around use. It forms a large, 20 inch-tall and 30 inch-wide clump, featuring rich gold, heavily crinkled, round leaves. Whitish mid-season flowers grow close to the foliage.

H. "Blue Cadet" a charming, small, blue hosta, makes a nice foreground or edging plant. The rounded, heart shaped leaves are 2 to 3 inches wide. Mid-season, this floriferous cultivar produces beautiful, mauve-blue flowers on erect 15 inch stems. Mature mounds are 15 to 18 inches in diameter and 12 inches tall.

H. Decorata is often incorrectly sold as H. "Thomas Hogg." Dark-green leaf blades, rounded at the tip and neatly edged in white, are borne on winged petioles. Deep blue, mid-season flowers contrast nicely with the variegated foliage. This rhizomatous hosta produces low-spreading mounds 8 to 10 inches tall, making it an ideal massed ground cover or accent plant.

H. fortunsi "Aureo-marginata" is often incorrectly labeled "Gold Crown" or "Golden Crown." Mature plants have 6 to 8 inch-long, dark green leaves framed in rich gold borders. "Aureo-marginata" forms clumps 24 to 30 inches wide and 18 inches tall pale lavender flowers appear in mid-spring. This hosta seems to tolerate a wide range of growing conditions and holds up well until late in the growing season.

H. "Gold Edger" A compact growth habit (6 inches tall and 12 to 15 inches wide) and golden chartreuse leaves make this fast-growing cultivar an ideal edging for a bed or a path. Rounded, substantial leaves complement mid-season lavender flowers.

H. lancifolia Shoots appear in early spring, and this floriferous species produces late season, lavender flowers. Twelve to 14 inch-tall mounds form dense, uniform clumps.

H. "Royal Standard" is a regal hosta with rich, glossy green foliage. The vase-shaped, upright. 24 inch-tall habit makes "Royal Standard" a good background plant. This cultivar can handle more sun than most hostas.

H. sieboldiana "Elegans" is a very large hosta. Five to 6-year-old clumps produce mounds 6 to 7 feet across and 30 inches high in good growing conditions. The heavily textured and crinkled large round leaves have a nice blue sheen early in the season. The whitish flowers are very fragrant and appear early.

H. ventricosa provides rich, dark green, heart-shaped leaves with a velvety sheen not found in many hostas. Mature mounds are 30 to 38 inches wide and 20 to 24 inches tall. Deep blue flowers are borne on 36 inch stems in mid-season.

H. "Gold Standard" emerges green in spring but gradually changes to a lovely gold. The leaves are nicely bordered in blue-green. Some morning sun produces the beat coloration. "Gold Standard" can become a large 24- to 30-inch clump under ideal growing conditions. Its pale lavender flowers are insignificant when compared with the garden value of the leaves.

*Hosta variety information derived from Piccadilly Farms, Bishop, Georgia.

Status and Revision History
Published on May 15, 2009
Published with Full Review on May 11, 2012


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