Perfect for planting in shady areas, hostas (Hosta spp.) are flowering perennials that are popular in home gardens. While hostas are fairly easy to care for, brown hosta leaves are often an indication of a fungal foliar disease. Purchasing healthy plants can help prevent these conditions from arising, as can maintaining good cultural practices, like spacing out plants and watering them carefully.
Hosta Fungal Leaf Diseases
A common cause of irregular, rusty lesions on hosta leaves is a fungus called anthracnose. The lesions may be white or tan in color with a darker brownish border. Within the affected areas of the leaves, you may see small black dots, which are the fungus' fruiting bodies. This disease is more common in warm, humid conditions, which is why it is important to water hosta plants in such a way that the soil is moistened but the leaves remain dry.
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While anthracnose does not seriously harm a healthy hosta plant, it can affect its appearance. You can control this disease by pruning out infected leaves. The same strategy applies when it comes to leaf spots caused by other species of fungi. Applying a fungicide to the hosta leaves at the first sight of discoloration can also help to prevent these diseases from spreading to healthy parts of the plant.
Other Diseases of Hostas
In addition to foliar diseases, other types of pathogens can be the cause of hosta leaves turning brown. For example, the water molds that cause crown and root rot can result in leaf discoloration and eventually plant death. The same is true of petiole rot, which is caused by the fungus Sclerotium rolfsii var. delphinii. When planting hostas into a garden bed, handle the stems carefully, as fungi can enter the plant through wounds. Infected hosta plants should be removed and discarded.
Certain viruses that attack hostas can also cause parts of the leaves to turn a rusty brown color, including a pathogen known as the hosta virus X. This virus can be spread by insects or on garden tools. Hosta plants infected with this virus should be disposed of to prevent the disease from spreading. It is important to sanitize garden tools. Other plant viruses that affect hosta plants include tomato ringspot and impatiens necrotic spot.
Common Hosta Pests
Brown rusty lesions on a hosta plant may also be the work of foliar nematodes, which are microscopic organisms that resemble worms. In young plants, nematode feeding can cause new leaves to curl. Mature leaves may look brown and tattered.
It is therefore important to inspect hosta plants for any sign of nematode damage before introducing them into your garden. Skip plants with brown or yellow areas in between leaf veins, which is a symptom of a nematode infestation. In addition, it is important to keep hosta plants dry and avoid splashing water near them, as this is one of the primary ways that foliar nematodes spread. It is best not to take cuttings from infected plants.
Slugs are another common pest of hosta plants. While slugs will not lead to leaf discoloration, they can leave significant holes in the foliage.