GARDEN CAPSULE
The challenge: Your hostas started out as beautiful as ever this spring, but now the leaves have large irregular spots. The centers of some of the spots have fallen out and other leaves are dying back completely.
The solution: Blame a fungal disease called anthracnose, which often occurs when the temperature is warm and the leaves are wet for an extended time. For now, remove the leaves that are most damaged. In the future, try to head off this disease by maintaining a fresh but thin layer of mulch around plants, spacing plants for good air circulation, planting hostas only in well-drained soil and avoiding overhead watering. If problems persist, consider moving the plants to a place that gets a little early morning sun, so the dew will dry more quickly. Don’t mistake sunburn for disease; if hostas getting too much direct sunlight have bleached patches and thin dead areas, move them to a place with more shade.
Pluses: Anthracnose isn’t fatal to hostas; you can expect the plants to return next spring as pretty as ever. Despite disease and pest problems from time to time, hostas are normally easy to grow in shady gardens.
Minuses: By the time anthracnose appears, fungicides are of no use. Some varieties, such as Tokudama hybrids, are particularly suspect to anthracnose.
Sources: For detailed information on diagnosing and controlling problems with hostas, see “Sustainable Urban Landscapes Hosta Diseases and Pests” at store.extension.iastate.edu/ Product/sul14-pdf.