Disease on 'Cardianl' dogwood

Asked October 16, 2013, 8:15 AM EDT

The Cornus 'Cardinal' dogwood hedge that we planted for a client 5 years ago is dying is a slow death. In addition to leaf spot; the mostly older stems (canes) are turning dark brown--almost black then dying off completely. Half of the 10 we planted have died. Some of this discoloration is ''spotty'' along the stems and on others, it appears as ''rings.'' Is this stem canker or twig blight? Is there a way in which to control, if not eradicate this issue? Would it be safe to replant w/ the same cultivar or would they, too become susceptible? Thanks for your response. best, alan

Allegheny County Pennsylvania

1 Response

yellow-and red-twig dogwoods (Cornus sericea) are VERY susceptible to canker diseases caused by Nectria fungi. When these shrubs become drought-stressed, Nectria may kill much of the conductive tissue in dogwood stems, resulting in a blackened look to the stems or part of the stems. These dogwoods are NOT drought-tolerant and need moderate to high amounts of water. They should not be allowed to become drought-stressed summer or winter. Ideally, they should not be planted on hot S exposures unless they will receive plenty of water. During the dormant season, find affected stems and then: -follow stem down several inches to a few inches below blackened tissue -prune just above a bud, remove/destroy pruned stems -spray blades with Lysol between every cut that you make -mulch dogwoods to help retain soil moisture -water dogwoods well. Ideally, avoid repetetive leaf wetting with overhead irrigation - dogwood leaves may develop a leafspot disease when regularly wetted.

Robert Cox Colorado State University Extension Arapahoe County