Cause Seiridium cardinale (formerly Coryneum cardinale), a fungus. Monterey cypress (Cupressus macrocarpa) has the worst damage, but other Cupressus spp. also are affected. Spores are rain splashed; the fungus also can be moved on pruning tools and infected nursery stock. It enters trees through natural occurring wounds or insect damaged tissue. Favored by prolonged periods of mist and light rain with moderate temperatures. Cankers enlarge faster on drought-stressed trees. The fungus can infect many genera of the Cupressaceae including Chamaecyparis, Juniperus, and Thuja, as well as hybrids such as Leyland cypress. A different species of Seiridium may be involved with cankers of Port Orford cedar in Oregon. Cupressus glabra, C. lusitanica, and C. torulosa are more resistant although not immune.
Symptoms Old foliage yellows and browns in spring, followed by a fading green or death of new foliage. Small branches are infected first, then larger ones. A typical lens-shape, sunken canker can be found on the branch below affected foliage. Top death and dieback are common. Bark turns brown, and small, black fruiting bodies (acervuli) may form in the cankered area. Drops of resin frequently are in and at the sides of cankers. The expansion of cankers is slow on large branches and trunks of mature trees. Could be confused with Monochaetia canker.
Cultural control
- Plant resistant cultivars.
- Remove and destroy affected branches 1 to 2 ft below the canker. Sanitize pruning tools between cuts.
- Avoid water stress and wounding trees.
Chemical control Use before fall rains.
- Cleary's 3336 EG at 16 to 24 oz/100 gal water. Group 1 fungicide. 12-hr reentry.
- CuPRO 5000 at 1.5 to 5 lb/A but only up to 2 lb/A when new growth is present. Group M1 fungicide. 48-hr reentry.
- Mancozeb-based products can be used and may provide some protection. Group M3 fungicides. 24-hr reentry.
- Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.
References Danti, R., Barberini, S., Pecchioli, A., Di Lonardo, V., and Della Rocca, G. 2014. The epidemic spread of Seiridium cardinale on Leyland cypress severely limits its use in the Mediterranean. Plant Disease 98:1081-1087.
Graniti, A. 1998. Cypress canker: A pandemic in progress. Annual Review of Phytopathology 36:91-114.