Key Features
- Wilt, yellowing or leaf scorch
- Uniform dieback in the canopy
- Rot or fungal webs at crown
Symptoms
Crown rot describes the decay of a stem or trunk at the soil line by a soil-borne pathogen. Destruction of vascular tissue results in discoloration and wilting of leaves, leaf-drop, and blight. Eventually, the plant will die. Plants may have a canker at the soil line, while hosts with succulent stems will have a dark band that encircles the stem between healthy tissue and the rotting crown. Canopy symptoms progress from the top of the canopy down due to a lack of water and nutrients. The pathogen spreads up the stem as the host is weakened. The weight of the canopy often causes the stem to break at the crown. Small crops will simply bend to the ground. The trunks of affected trees may break unexpectedly. Send samples to a plant disease diagnostic lab for analysis before attempting control measures. Contact the lab for information on what material to submit.
Biology
A diversity of soil-borne pathogens are present in most soils. These pathogens can successfully infect when provided the proper environmental conditions and/or a wounded host. The disease progresses up the stem from the site of infection. Succulent stems may be girdled by the disease, while woody stems and trunks have isolated, spreading cankers.
Management Recommendations
Disease prevention must be the primary goal as fungicides cannot "cure" these diseases. When planting and working in the landscape, take care to not damage the crown or roots of any plants. Plant to avoid infection. Choose sites well suited to the plants' soil, sunlight, and water requirements. Irrigate and fertilize as necessary to reduce plant stress. Anything that spreads contaminated soil (such as workers, run-off, pets, and insects) effectively spreads soil-borne pathogens. Inspect plants for symptoms prior to purchase to decrease the chances of introducing the fungus to new plantings. Always remove infected plants as soon as possible to prevent inoculum from building in the soil. Replant with non-hosts, as even resistant varieties can be killed if inoculum levels are high. Varieties of some ornamentals are more resistant to certain crown rot pathogens. Consult a local nursery or arborist for more information.
Effective Pesticides
Active Ingredients include: Phosphorous acid salts, Thiophanate-methyl
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