Hostas are true shade-lovers. If you want to add color and texture to a shady part of your garden, this is your plant. While they’re usually pretty tough, like all plants, hosta plants can suffer from a variety of pests and diseases.
As long as the soil isn’t heavy clay, hostas generally thrive. They love rich, organic soil, dappled sunlight, or full shade. You can grow hostas outside in the garden, outside in containers, and as a potted plant inside.
But when problems strike, you need to know how to address them quickly, so let’s jump right in.
How To Make Hostas as Pest and Disease Resistant as Possible
Before we talk about how to recognize and deal with pests and diseases of hosta plants, we should talk about how to avoid them altogether. Keeping a plant in optimum condition is the best way to help to avoid pests and diseases. It also saves time and money.
Green leaf hostas tolerate more shade than the variegated types, which require around four hours of dappled sunlight throughout the day. Blue types do best in full shade. The yellow varieties like a little more sunlight, up to six hours of dappled light per day.
It’s a good idea to find out what your variety of hostas likes to make sure they don’t struggle.
Hostas love plenty of water, especially if they’re in containers. They also like being fertilized regularly. Use a slow-release fertilizer at the beginning of spring, and then every three weeks with a liquid fertilizer, if necessary.
For potted hostas, consider repotting at the beginning of the growing season because they get root bound quickly.
8 Common Pests
For the most part, pests don’t seem to bother hostas all that much except for one particular pest, and you can probably guess what that is. If you said slugs and snails, you’re right. Here are all the critters that might come to call:
Aphids will sometimes feed on hostas, though you’ll typically only see them on stressed plants. Head to our guide to learn how to identify and eliminate aphids when they strike.
While aphids might not kill your hosta themselves, they spread diseases, so you want to keep them away.
2. Slugs and Snails
This is one of the most common problems hosta growers talk about. Slugs and snails love hostas and will feast on them at night. They eat small holes in the leaves and leave slimy trails over the plant.
Use whatever methods you prefer to rid your hostas of slugs and snails. I prefer pellets. Some prefer beer traps or regular sprays of neem oil.
3. Black Vine Weevil
Another pest that affects the leaves is the black vine weevil (Otiorhynchus sulcatus). They chew holes or notches on the outside of the leaves.
Weevils can come into your greenhouse, garden, or even your house to get to your plants. The larvae are generally the most damaging to hostas. The larvae overwinter in the soil around the base of the plants. They feed on the roots and crown of hostas.
Large infestations, which are more common in the summer, can completely destroy your plants.
If you notice the leaves begin to wilt and go yellow, it could be the larvae of black vine weevil. The larvae eat their way through the roots. This causes the leaves to die and wilt and appear dehydrated. They will also girdle the stem of hostas just below the surface of the soil.
They change to pupae and then adults in the spring and emerge from the soil to start the life cycle all over again.
First, remove any hosta leaves that are dead or show diseases. Then, do the following:
- Don’t overwater hostas because the larvae of black vine weevil love moist soil.
- Remove wet mulch from around the base of the plant.
- Black vine weevils walk from one plant to another. Use diatomaceous earth or a sticky barrier to trap them.
- Use an organic insecticide.
4. Foliar Nematodes
Foliar nematodes (Aphelenchoides fragariae) are tiny roundworms that cause disease by infecting hostas, much like bacteria.
Foliar nematodes are tiny, so you can’t easily identify them with the naked eye. Plus, they feed inside the leaves. So how can you tell if they’re the cause of your hosta woes?
In late summer, if you see what looks like stripes on the leaves, it could be caused by nematodes. The plant may also look dried up and tatty.
You should be able to remove the infected leaves and destroy them in a fire or remove them from the property. Don’t splash the leaves as you water because this spreads the foliar nematodes. Water at the soil level.
5. Root-Knot Nematodes
When these microscopic pests are present, you’ll see galls or swollen lumps on the roots. Of course, you’re probably not watching the roots of your plants, so you have to look at what’s happening above ground.
Initially, you may notice the plant has stunted growth even if it is well-fed or in healthy soil. Because the pests themselves are invisible to the naked idea, this is sometimes mistaken for a disease on hosta plants rather than a pest.
When you dig the hostas up, you will notice the galls and may also see extensive branching of the roots at the tip of existing roots. Remove and destroy these plants and don’t plant hostas again in this area.
Our article can help you figure out how to restore your garden once you have these pests.
6. Blister Beetles
Adult blister beetles eat the leaves, stems, and flowers of hostas. The larvae, which look like grubs, eat the roots. The best way to get rid of the adults is to handpick them off and drop them into soapy water.
In the spring, gently turn the soil around the plant to expose the eggs and larvae for birds to feast on. Spray the plant with an all-purpose insecticide and then head to our guide for more tips.
Cutworms (typically Peridroma saucia) usually get in hostas that are planted in sunnier spots rather than those in shady positions. You often see leaves eaten around the edges at night. Cutworms live in the soil around the base of hostas or close to them in any weeds you have allowed to grow.
Although not a major threat to hostas, cutworms can make them look damaged and tatty.
Keep weeds well away from your hostas and sprinkle diatomaceous earth around the stems. You can also sprinkle a small amount of bran meal or cornmeal on the soil. As little as a half to one teaspoon is sufficient.
Although not a common pest of hostas, grasshoppers will damage them severely if they start to eat them, so you need to be extra alert. If you see even one of these critters in your garden, head to our guide to learn how to deal with them before they take over.
5 Common Diseases
Healthy hostas are better able to resist pests and diseases, so do your best to keep your plants as robust as possible, as we discussed above. However, if diseases find their way to your garden, don’t lose hope. You can deal with most problems fairly easily.
1. Petiole Rot
Leaves at the soil level will start to turn yellow and then brown, before wilting completely and dying when this hosta disease is present. An infected leaf will drop off at the lightest of touches.
You will see fan-like white growth at the base of the hostas and eventually black dots the size of mustard seeds start to form.
Originally called hosta crown rot, this is caused by a fungal pathogen called Sclerotium rolfsii var. delphinii and it’s serious.
To prevent petiole rot, move any mulch away from the stem of the plant and maintain good watering practices. That means you shouldn’t overwater or underwater, and irrigate at the soil level, not on the foliage.
Remove infected plants immediately and either burn them or discard them in a sealed garbage bag. If you remove an infected plant, you will also have to remove the surrounding soil to a depth of around six inches.
Home gardener strength fungicides don’t work against this fungus, so prevention is the best option.
2. Hosta Virus X
With hosta virus X (HVX) will see a yellowing mosaic pattern on the leaves before the rapid death of foliage. On the variegated types, the multiple hues will bleed into each other.
This annoying virus is spread by your hands, the garden tools you use, and insects. You should wash and disinfect the tools and your hands before moving from one hosta plant to the next.
Once your hosta is infected with this disease, there isn’t anything you can do to fix it.
Never divide infected plants because you will just spread the virus. Infected plants should be destroyed.
3. Bacterial Soft Rot
Bacterial soft rot is caused by Erwinia carotovora subsp. carotovora, E. carotovora subsp. atroseptica, or E. chrysanthemi.
You know when bacterial soft rot is occurring thanks to the smell. It’s awful, like rotting plants. When it attacks, the leaves and petioles wilt and die.
The bacteria is common and is present in both soil and water. Basically, it’s an infection causing necrotic spots that look like a creamy spot surrounded by a darker ring. The smell appears as the spots rot.
There is no treatment for this so you are best to avoid it through hygienic garden practices.
Avoid sopping wet conditions. Make sure you don’t overwater and the ground is well-draining.
When weeding, transplanting, and planting, make sure not to damage the hostas to avoid allowing the bacteria into the plant.
4. Fusarium Root and Crown Rot
Fusarium root and crown rot is a disease caused by fungi in the Fusarium genus, usually F. hostae. The first sign of this is often on the stem at the soil line. You will see a brown to black line where the plant is beginning to rot.
The leaves will go yellow and die, and you may notice the entire plant is stunted.
This fungal infection can spread through root-to-root contact, from touching other infected plants, through the air on the wind, or by gardening tools.
Fusarium root and crown rot can look like many other infections, so to tell the difference look for a combination of:
- Seedlings and new plants that are yellow and often stunted
- The lower leaves turn yellow first, then drop off.
- Sometimes the plant dies after the yellow leaves drop off
- There is a brown to black rot girdling the stem just above the soil line
- The roots are distorted and discolored when you remove the dead or infected plant
- When you slice the stem lengthways after removing the plant there is a reddish to brown discoloration.
Control the chances of this fungal infection by maintaining a soil pH of 6.0 to 7.0. Remove any plants you suspect are infected straight away. Roots must be removed and disposed of as well.
This fungal disease affects many plants in the home garden and hosta plants are no exception. Read our article on how to identify and treat anthracnose here.
Lots of herbivores love hostas. They’re actually edible and nutritious for humans as well as animals like deer, voles, and rabbits. Fencing is generally the best deterrent, though you might consider growing your hostas in containers on your patio if the animals are really persistent in your area.