Hostas are gorgeous ornamental plants that can bring a touch of succulent beauty to any garden. While they’re generally hardy, these plants can be vulnerable to leaf-eating pests and insects that threaten their health.
If you notice any visible damage to your hosta, it’s time to take action! Treating diseases as soon as they appear is crucial because waiting too long could mean the plant won’t make it.
But don’t worry! I’ve got your back. I’ll share some common hosta diseases with you and real-life pictures of pests and diseases that can affect your plant. With my tips, you’ll know how to identify and treat issues before they become a bigger problem.
So, what are the most common diseases that affect hostas? Let’s take a look together!
-  Hosta Virus X (HVX)
-  Phyllosticta Leaf Spot
-  Gray Rot
-  Root, Stem, and Collar Rot
-  Bacterial Soft Rot
-  Anthracnose
-  Crown rot (Southern Blight)
- Other Diseases to Be Aware of
 Hosta Virus X (HVX)
American scientist Lockhart discovered Hosta Virus X (HVX).
The disease is spread by sap on garden tools or hands while pruning or dividing shrubs.
When you use a dirty hoe or your hands to touch healthy plants, the virus enters the plant’s tissue through the cuts and wounds and begins to feed and multiply.
Before the discovery of the virus, yellow spots, tiny flecks, dashes, and rings were mistaken for unusual hosta coloration.
However, it was later discovered that it is a disease that causes stunted growth and curling leaves.
Hosta Virus X (HVX) distinguishing characteristics:
- The heterogeneous coloration of the leaf due to variations in tissue density and coloration;
- Dark green stripes on veins of leaf confirm hosta virus x infection.
- Chlorosis occurs, and as a result, the foliage turns a pale shade of green. Sometimes the vein starts turning yellow in an advanced stage.
- Small, fuzzy spots that look like a mosaic
- Stunted growth of the plant, resulting in dwarfism;
- The flowers’ color is faded, and no ovary can be found.
Immediate action: If an infestation is detected, the entire garden should be replanted as far away from the infected area.
The affected plants should be disposed of as household waste or burned to prevent the hosta virus from spreading to other plants.
Even though Hosta sieboldiana, also known as Siebold’s plantain lily, and its hybrids are virus-resistant, that doesn’t mean they’re entirely free of the risk of infection.
There’s no point in trying to save the plant if a virus has been found because the disease is incurable.
It infects every part of the hosta plant, eventually killing it. I recommend burning the diseased hosta and disinfecting the used tools.
Read this article about how to know for sure if you have the hosta virus before you do anything drastic.
 Phyllosticta Leaf Spot
Phyllosticta Leaf Spot, also known as brown spot disease, is a common problem for indoor and outdoor plants, including hostas. The Phyllosticta fungus thrives in environments with high humidity and temperatures above 77°F (25°C).
If you notice small, circular brown spots on your plant’s leaves, it’s likely a sign of Phyllosticta Leaf Spot. The spots may merge together, causing the leaf to wither and eventually die.
- Large brown spots appear on the surface of plant leaves.
- The spots gradually blend together to form a large lesion area.
- The fungus appears as a white or yellowish plaque on the surface of the spots.
- The disease frequently affects both the leaves and the flower stems of hostas.
- Infected plants gradually dry out and die.
- Brown spots appear on the leaves, which then crack and fall apart.
- The advanced stage of the Phyllosticta leaf spot leads to the death of the plant.
If you’re dealing with brown spot disease on your hostas, you’ll want to take action quickly. Here are a few things you can do:
- First, reduce the frequency and volume of watering your hosta to prevent the fungus from spreading. You can also try burning any leaves or stems with fungal spore centers to stop the disease.
- If the plant is severely damaged, discarding the entire thing to prevent the fungus from spreading to other plants in the area is best.
- To treat brown spot disease, copper-based fungicides can be effective. Just spray every 10 days until flowering begins for best results.
 Gray Rot
Gray rot fungi can be a real headache for gardeners, as they’re known to attack a range of plants, including your beloved hostas. Worse, the disease can be deadly for your plants if you don’t take quick action.
The botrytis fungus spreads by growing mycelium on your hostas and releasing spores that can travel on the wind to nearby plants. That’s why taking prompt measures is crucial if you notice any signs of gray rot, such as wilting leaves or gray, fuzzy patches.
To prevent the disease from spreading, removing any affected leaves or stems and disposing of them properly is essential. Ensure your plants have good air circulation and avoid overwatering them, as excess moisture can encourage the growth of the botrytis fungus.
Gray rot can manifest in different ways depending on the stage of the disease:
- In the early stages, you may notice blotchy, deformed, dried leaf edges, tips, and visible Botrytis spores.
- As the disease progresses, the hosta’s leaf tips may decay.
- The rot can spread to every part of the leaf in advanced stages.
If you notice any of these symptoms, it’s crucial to take action immediately. Treatment may involve spraying fungicides on the affected leaves in the early stages.
However, if the infestation is severe, you may need to destroy the entire plant to prevent the disease from spreading to other plants in your garden.
Preventing gray rot is essential to keep your hostas and other plants healthy. It’s much easier to prevent the disease than to treat it once it has taken hold.
To prevent gray rot from infecting your hostas, here are a few tips you can follow:
- Apply the first soil treatment early in the spring when the soil is still loose. This can help eliminate any overwintering fungi and prevent the disease from taking hold.
- Consider using a copper-based contact fungicide to protect your plants. You can spray the fungicide on planting sites using a sprayer. This can help prevent the fungus from growing and spreading.
 Root, Stem, and Collar Rot
Phytophthora is a type of fungal rot that can be a real problem for your hostas. This fungus lives in the soil and can attack your plants by infecting the roots and rhizomes.
One of the tricky things about Phytophthora is that it can remain inactive in cold weather, only activating when the environment becomes warmer and more humid. This makes it all the more important to take preventative measures to protect your plants.
If you notice signs of Phytophthora, such as rotting or wilting leaves, it’s essential to take action immediately.
Unlike bacterial soft rot, which can quickly take over and destroy your plant, Phytophthora tends to progress much slower. This means you may have a better chance of saving the affected pieces.
Dealing with root rot can be a real challenge, especially since it’s difficult to spot in the early stages. But there are a few things you can look out for that may help you identify the problem.
One of the telltale signs of root rot is discoloration of the leaves. You may notice that the leaves turn yellow from the edges to the center before eventually discoloring and drying out, causing them to fall off.
Unfortunately, it’s nearly impossible to predict root rot before it starts without inspecting the root system. If the roots have begun to rot, you may notice symptoms appearing above ground.
Dealing with hosta root rot can be a real challenge, and unfortunately, there are some conditions for which there is no known treatment.
Here are some tips for dealing with this condition:
- Do not use soil beneath the infected plant; avoid transplanting shrubs suspected of infection.
- To prevent the fungus from spreading, remove all diseased hostas from your garden and dispose of them properly.
- If caught in the early stages, you may be able to treat the problem by digging up your hosta and removing any soft roots and rhizome material that isn’t hard and white. After cleaning the plant, use hydrogen peroxide a few times and let it dry thoroughly in the sun.
- You can also use systemic fungicides like Liquid Copper Fungicide or Phyton to treat the problem.
- If the infestation is severe and cannot be treated, you may need to dispose of the entire plant and the surrounding soil to prevent the fungus from spreading.
Copper Sulfate And Bordeaux Liquid Spraying Are Effective
However, risking the plant’s health is not a good idea. When the first leaf turns yellow, dig up the hosta and thoroughly examine for any signs of root rot.
Cut the affected areas with a sharp knife, and treat the cuts with fungicides or crushed activated charcoal.
Do not replant the diseased hosta until it has dried out for 1-2 hours, and then plant it in a new container.
 Bacterial Soft Rot
Bacterial soft rot is a condition caused by various bacteria and often occurs when a leaf has been damaged.
This can result from various factors, including winter icing that causes wounds on the leaves.
Typically, the symptoms of bacterial soft rot become more noticeable during the warming period after a frost.
As bacterial soft rot progresses, you may notice some distinct signs that indicate the plant is infected.
For instance, decaying cuttings and lower leaves will emit a pungent odor that is hard to miss and a clear indication of the infection.
Additionally, you may observe visible damage to the plant, such as new brown spots on the hosta’s leaves.
If you have identified a bacterial soft rot infestation in your hostas, it’s crucial to act quickly to prevent the bacteria from spreading to other plants. Here are some steps you can take:
- Remove any infected hostas and dispose of them properly.
- Thoroughly clean any tools that came into contact with the infected plant, and wash your hands and gloves.
- Because the bacteria tend to spread slowly and only affect the damaged areas, there’s usually no need to remove the entire garden.
Bacterial soft rot can spread quickly and affect healthy leaves and neighboring shoots if left untreated.
This condition is known to be widespread and can be especially damaging to certain plant species that require plenty of shade and moisture to thrive.
One way to identify a bacterial soft rot infection in hostas is to look for small, round-shaped brown spots on the leaves that tend to grow larger and develop darker borders, much like rust on a plant.
These spots can cause the leaf to appear torn, with only the tougher veins remaining intact.
To combat a bacterial soft rot infection in your hostas, there are a few steps you can take.
First, remove any diseased leaves from the plant and provide plenty of room for air circulation to help reduce humidity levels. This can help prevent the bacteria from spreading and keep your plants healthy.
Next, consider using a fungicide to treat the remaining healthy leaves and help prevent them from becoming infected again.
 Crown rot (Southern Blight)
Petiole rot, or crown rot, is a fungal disease that can be particularly dangerous for plants. This condition is caused by a fungus known as fusarium, which can cause the roots of the plant to rot from within.
While this may not initially seem significant, the problem becomes much more serious when the fungus reaches the plant’s crown. At this point, you may need to cut out the affected area until you reach clean tissue.
Fusarium can be particularly problematic in potting soil that dries out too much between waterings, but it typically only becomes a serious issue when it has somehow made its way onto the plant or soil.
You may notice a few telltale symptoms if your hostas are affected by petiole rot. The plant leaves may start to yellow and wilt along the outline, and the base of the leaf may become floppy, spongy, and rotten.
In some cases, the leaves may become too large to support themselves and fall off the main shrub altogether. You may also see white fungal filaments, or mycelium, growing on the plant.
Over time, the fungus can spread and produce small, round sclerotia seeds, eventually covering the entire plant.
While the fungus may be dormant during colder weather, it can come to life when the temperature and humidity levels rise.
Unfortunately, there is no known treatment for petiole rot in hostas. If you are replanting, it is best to avoid using old soil that may be contaminated with the fungus.
To prevent the disease from spreading, it’s important to eliminate or destroy any infected hostas in your garden.
With the information on common hosta diseases and their symptoms, you should now be better equipped to identify and treat issues that may arise with your plants.
Other Diseases to Be Aware of
Tiny nematodes, about 2 mm in diameter and round can cause brown spots and stripes on hosta leaves. Unfortunately, detecting a nematode infestation in the early stages of the disease can be difficult.
If you suspect that your hostas may be affected by nematodes, there is a simple test that you can perform to confirm the diagnosis.
Start by chopping a leaf and placing it in water for 15 to 20 minutes. If nematodes are present, they should be visible in the water when viewed under bright light.
Nematodes live as parasites in the plant’s tissues, causing the plant to become misshapen and spreading harmful viruses.
Nematodes are hard to eliminate because pesticide sprays kill adults, not eggs.
To get rid of the pest, use this ready-to-spray nematode control solution.
In addition, you must adjust the watering schedule for your hosta if you want it to grow correctly and without issues.
Tobacco Rattle Virus
TRV is a virus that commonly affects Hostas in North and South America and Eurasia, with up to 400 different varieties impacted.
The virus is transmitted by leaf nematodes that can harm hostas. Symptoms of an infestation may include:
- Smaller leaves with mottling, dead spots, and wavy edges.
- Veins and stems of the plant may rot.
- Dwarfism and inhibited growth.
- Shortened cuttings and branches.
- Nematodes may also damage rhizomes.
The severity of symptoms can decrease when temperatures exceed 68°F.
Leaf Curl Virus
Curl viruses can cause severe damage to hostas, resulting in curled leaves, small leaf sizes, and star-shaped spots. With time, the spots turn into holes due to cell death.
Unfortunately, this virus has no known cure, and infected plants must be removed and disposed of properly.
It is crucial to disinfect the soil and any tools used during removal to prevent further virus spread.
Rust on Hosta
Hosta varieties with a disease known as “rust” may have yellow rings around their leaf margins. Large yellow spots that eventually turn rusty in color are typical symptoms of the disease in its early stages.
Lack of humidity is often the main cause of rust disease. To combat this disease, increase the plant’s watering, monitor water quality, and spray the plant in the morning or evening when the sun is less intense.