Shade tolerant and easy to grow, hostas are often used as border plants for home landscapes. Hostas have large, colorful foliage that may be solid or bi-colored, including combinations of blues, golds, greens or blues. Variegated varieties are also available. Hostas are clumping perennials that should get regular water, but they can be susceptible to fungal diseases, particularly if planted in areas that retain water. Soil-borne fungal diseases are of particular concern.
Caused by a fungus, anthracnose is the most common disease that afflicts hostas. The key symptom is the appearance of spots with dark borders on the leaves. The centers of the spots may fall out, giving leaves a ragged appearance. Leaves may die back, and infected leaves should be removed. Anthracnose is rarely fatal and may be treated with a fungicide. Preventative measures include making sure the plant is watered early in the day and kept cool.
Fusarium Root and Crown Rot
Fusarium root and crown rot is a fungus that attacks the roots and crowns of hostas by entering the plant through sores or open wounds. Dry soil is a breeding ground for this soil-borne fungus, which thrives when temperatures are between 60 and 80° Fahrenheit. The key symptom of fusarium root and crown rot is shriveled foliage. The leaves will first turn yellow, then brown, and will dry out, as they are not getting adequate water through the root system. There is no effective treatment for plants with this disease, so infected plants should be removed. Soil may be treated with a fungicide.
Petiole rot is also caused by a fungus and can kill a hosta. Petiole rot, which is most common during hot, wet periods, attacks the outer leaves first. Leaves will turn yellow, then brown, and begin to wilt. Infected foliage is easily pulled from the plant as the petiole, or stem area, has rotted and may be soft. Infected plants should be treated with fungicide or removed. This fungus lives in the soil and can remain dormant for long periods. To avoid petiole rot, mulch the area around hostas and keep the soil moist.
Similar to petiole rot, root rot is caused by a fungus that lives in the soil. But this fungus attacks the roots of the plant, which are then unable to provide adequate nutrients and water to the foliage. The leaves will have water spots, usually near the the area where the leaf blade meets the petiole, or in any other area where the leaves collect water. Infected plants should be removed, and soil may be treated with fungicide to prevent future infection. To avoid root rot, do not plant hostas in areas that retain water.