You walk outside to your garden to see how your garden is growing when you stop in your tracks. That beautiful hosta that looked healthy several days ago is now sprawled out on the ground with browning leaves. With careful inspection you find that the stems at ground level are no longer attached to the plant. Your hosta has crown rot! Crown rot is a fungal disease caused by Sclerotium rolfsii and it can severely damage established hostas within a week. Crown rot was normally found in the southern United States, but it is now found in Midwest gardens. Crown rot starts during prolonged hot, humid weather. In my zone it has been very hot, very humid and with lots of rain. Perfect conditions for this disease.
The bottoms of the petioles are brown, mushy and you will find some small white to rust colored spheres, called sclerotia, which are about the size of a mustard seed. Sclerotia can survive cold winters. Also present will be fluffy white threads (mycelium) on the crown of the plant and the soil. Mycelium produces sclerotia. There is no dormacy period for sclerotia and it can be dormant in the soil for years till the conditions are just right. When S. rolfsii mycelium comes in contact with a plant, it produces oxalic acid that destroys the tissue of the petioles of the plant which causes the hosta to collapse on the ground. Crown rot is spread by purchasing plants containing it or trading plants with fellow gardeners that are infected. Sclerotia can spread on your shoes or tools and spread to other parts of the garden. It can also spread by rain splash or irrigation splash.
How do you get rid of S. rolfsii? You can slow or stop the spread by:
- Carefully inspecting plants that you purchase or trade with others.
- Practice good sanitation habits in the garden to reduce it's spread. Clean up damaged leaves and discard in a plastic bag to the trash. Do not compost leaves. Clean up all your hosta leaves after the first frost.
- Provide a mulch free zone of several inches away from the crown of your hosta.
- Clean and sanitize gardening tools used around diseased plants. Dipping tools in a 10 percent bleach solution for a few minutes will kill S. rolfsii.
- You can dig down 8 inches and remove the soil from the contaminated area and replace with new soil.
- Apply a fungicide recommended for S. rolfsii and that can be used on hosta plants.
Be aware that S.rolfsii also effects over 200 other plants and not just hosta.
Happy Gardening!
The Creative Gardener