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Crown Rot

Plant disease

Description​

Crown rot is a general name for decay at a plant’s crown: the junction where stems meet roots, usually at or just below the soil surface. It is not a single disease with one scientific name. Depending on the plant, it may be caused by fungi or fungus-like water molds, including species of Phytophthora, Rhizoctonia, and other pathogens. Infection damages the tissues that carry water and nutrients between roots and shoots. Affected plants may wilt even when the soil is moist, grow slowly, or develop yellowing leaves. The crown can become soft and dark or develop a sunken, discolored lesion; roots may decay as well. Symptoms often appear after prolonged wetness or in poorly drained soil, although the conditions that favor disease vary by pathogen. Crown rot can affect seedlings, herbaceous plants, and woody ornamentals. Severe infections may girdle the crown and kill the plant.

Symptoms​

  • Wilting
  • Yellowing leaves
  • Stunted growth
  • Leaves dropping
  • Soft or rotting stems
  • Brown, mushy roots

How to Identify​

Inspect the stem at the soil line and gently expose the upper roots. Crown rot typically produces brown or black, softened, or sunken tissue at this junction; the discolored area may extend around the stem. Check whether nearby roots are firm or decaying. Unlike simple underwatering, a plant with crown rot may wilt while its soil remains moist, and watering will not restore it. Waterlogging without infection can look similar, so visible decay alone may not identify the cause. Some pathogens produce distinctive fungal growth, but many do not. For valuable plants or recurring losses, submit crown and root samples to a plant diagnostic laboratory before choosing a pathogen-specific treatment.

Prevention​

Start with healthy plants and place them in soil that drains well; use raised beds or improve drainage where water collects. Keep the crown at the appropriate planting depth rather than burying it under extra soil or mulch. Water according to the plant’s needs, allowing the surface to dry when appropriate, and avoid keeping the crown constantly wet. Space plants for airflow and remove weeds or dense debris around their bases. Clean tools and containers before reuse, and do not move soil from diseased plants into clean areas. Remove badly affected plants and their decaying roots promptly. Where crown rot has occurred before, choose resistant varieties if available, and avoid replanting a susceptible host in the same spot until the cause is known.

Treatment​

First, correct conditions that keep the crown wet: reduce unnecessary watering, improve drainage, and pull mulch or piled soil back from the stem without exposing roots excessively. Check the crown. If decay is limited and the plant is otherwise vigorous, better growing conditions may help it survive, but rotted tissue will not recover. Remove and dispose of plants with extensive crown decay or persistent wilting; include as much of the affected root system as practical. Do not compost diseased material unless your composting process reliably kills plant pathogens. Clean tools and pots before using them elsewhere. Avoid replacing the plant immediately in the same contaminated soil. Fungicides are not a general cure: products effective against water molds may not work against true fungi, and results depend on early, accurate diagnosis. If losses continue, identify the pathogen and use only a product labeled for that host and disease, following its directions.

Plants Affected​

Asparagus, Delphinium, Gerbera Daisy, Hosta, Pineapple, Water Lily, Wheat

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