The 2012 ASHS Annual Conference

Golden Canker is a common disease that frequently attacks pagoda dogwood (Cornus alternifolia L.) causing branch dieback, diffuse cankers, and occasionally stem mortality.  The causal agent, Cryptodiaporthe corni (Wehm.) Petrak, is commonly found throughout much of the northcentral and eastern United States.  An evaluation of 40 asymptomatic stems of pagoda dogwood from five natural stands and managed landscapes across Minnesota was completed.  Surface sterilization was used to eliminate contamination of microorganisms on the stem surfaces.  Results indicate that the fungus lives as an endophyte before becoming pathogenic.  When all sites were combined, the fungus was found in 62.5% of the asymptomatic stems studied.  A positive correlation between stem diameter and presence of the fungus was found. Discovery of a high percentage of asymptomatic stems, which were infected in the managed landscape (44%), suggests controlling the disease will be difficult.  Furthermore, these results suggest that removal of infected tissue may simply reduce the visual impact of the disease without impacting the future disease incidence of the pathogen on the infected plant.  Factors inciting a change in the fungus from a latent to active form of infection need to be investigated.