Hostas are herbaceous perennials prized for their ability to grow in shaded areas. Grown for their attractive foliage, they range in color from simple green leaves to a wide variety of yellow or white patterns, brightening shaded areas with minimal care. Although hostas are relatively disease free, they can be infected with several common plant diseases.
Hostas are subject to both fungal and viral infections that result in plant damage. Anthracnose, caused by fungi in the soil, causes leaf damage. Petiole rot quickly infects and kills hostas. Phytophthora foliage blight and root rot are caused by a fungi-like microorganism that breeds in the soil. Fusarium root and crown rot, caused by the Fusarium fungi, causes damage and death if not treated properly. Bacterial soft rot affects the soft tissue of foliage and may result in death.
Several viruses also infect hostas, but generally do not kill the plants. These viruses cause browned leaves and detract from the appearance of hostas.
Hosta disease results primarily from improper care and exposure to infected soils or plants.
Anthracnose presents with irregular spots with darker borders on foliage. As the disease progresses, the centers of the spots disintegrate, leaving tiny holes in the leaves.
Petiole rot causes foliage to yellow and then turn brown from the outer edge toward the base of the leaf. Eventually leaves wilt and fall from the plant. The base, or petiole, of the leaf softens and turn brown.
Foliar blight appears as large water-soaked areas on leaves that may expand to cover the entire leaf. Centers brown, dry and become brittle, while the outer leaf may maintain the appearance of watery spots on the leaf.
Root and crown rot causes stunted growth and wilting of leaves despite adequate water supply. The crown of the plant and roots discolor and begin to decay. Bacterial soft rot affects the plant tissue, causing yellowed wilting leaves and rotting stems accompanied by a fishy odor.
Viruses affect the appearance and reduce growth, but generally do not harm the plant.
Treatment for diseases related to fungi consists of applying fungicide to the soil, removing dead or diseased foliage regularly and keeping plants cool. Viral infections may require destroying the entire plant to prevent the virus from spreading to new plants.
Practicing good plant care techniques prevents most disease. Provide hostas with well-drained soil, avoid overwatering and keep mulch away from the base of the plant. Remove plant debris regularly and provide plenty of space for individual plants. Overcrowding invites both insect pests and sets the stage for disease.