Cylindrocladium Diseases: Root Rot, Canker & Leaf Spot on Woody Ornamentals

Cylindrocladium species attack over 100 woody ornamentals—azaleas, rhododendrons, camellias, junipers, white pine, holly—and many foliage plants (asparagus ferns, palms, Spathiphyllum). Depending on host and species, they cause damping-off, wilt, root rot, stem canker, crown rot, or leaf spot.

Host-Specific Symptoms

Azalea

Outer root cortex dies; vascular discoloration extends ~1″ above soil line. Wilting even in mature plants. Leaves brown/black, drop. Cuttings may rot at base but root above rot—often die after potting.

Rhododendron

Stem and crown cankers.

White Pine

Seedling damping-off; root and stem cankers.

Holly

Tiny chlorotic spots become purplish-black with light green halos. Leaf drop even with few spots. Twig dieback if defoliation severe.

Ferns (Polystichum, Dryopteris, Nephrolepis)

Reddish-brown spots at petiole bases; brown-black spots with yellow halos.

Spathiphyllum

Older foliage wilts/yellows; roots die (plant pulls easily). Sunken black spots at petiole bases; leaf spots with yellow halos.

Favorable Conditions

Humid, warm (75–80°F / 23–27°C), overhead irrigation. Over-fertilization and other stresses contribute.

Nursery Management

• Plant Cylindrocladium-free seedlings
• Pot in sterile mix
• Propagate only from healthy stock (spreads rapidly in propagation beds)
• Rogue out and destroy infected plants
• Rake and destroy fallen leaves
• Protective fungicide applications (contact Extension for current list)
• Avoid overhead watering

Home/Commercial Landscape

• Remove and destroy severely affected plants

Scientific Reference

Crous, P.W. 2002. Taxonomy and Pathology of Cylindrocladium (Calonectria). APS Press. 294 pp.