Fungi belonging to the genus Cylindrocladium attack over 100 woody ornamentals including azaleas, rhododendrons, camellias, junipers, white pine, and holly. Many foliage plants including asparagus ferns, palms, and spathiphyllum are susceptible as well.

Depending on the host plant and species of Cylindrocladium involved, damping-off, wilt, root rot, stem canker, crown rot or leaf spot may occur.

Symptoms

Azalea

Outer root tissues die and root vascular tissue is discolored. Discoloration of vascular tissue may extend 2.5 cm (1 in) above soil line but seldom more. Root rot results in wilting even in plants several years old. Leaves turn brown and black and then fall. Cuttings may rot at base but roots develop above the rot. These plants often die after potting.

Rhododendron

Stem and crown cankers form.

White Pine

Damping-off of seedlings. Root and stem cankers develop.

Holly

Very small chlorotic leaf spots become purplish-black in color and have a light green halo. Leaves fall even if only one or a very few spots form. Twig dieback occurs if defoliation is severe.

Ferns (Polystichum, Dryopteris, Nephrolepis)

Reddish-brown leaf spots form at the base of petioles. Brown to black leaf spots have yellow halos.

Spathiphyllum

Older foliage wilts and yellows. Roots die allowing the plant to be easily removed from the soil. Sunken black spots form at the base of petioles. Brown to black leaf spots have yellow halos.

Cylindrocladium

caused diseases are favored by humid, warm, 23-27°C (75-80°F), conditions and overhead irrigation. Over-fertilization and other plant stresses may contribute to the problem.

Management Nursery

• Plant Cylindrocladium-free seedlings
• Pot in sterile mix
• Propagate from only healthy stock plants since the disease spreads rapidly in most propagation beds
• Rogue out and destroy infected plants
• Rake and destroy fallen leaves

• Apply a fungicide to protect healthy plants (Contact Cooperative Extension to obtain a list of fungicides currently recommended for use.

• Avoid overhead watering

Home or Commercial Planting

• Remove and destroy severely affected plants

Indepth, scientific treatment of this organism

• Crous, P. W. 2002. Taxonomy and pathology of Cylindrocladium (Calonectria) genera. 294 pp. 320 b & w illustrations. APS Press. 1-800-328-7560) $69.00.