Stems show similar symptoms as seen in Figure 5 with a canker at the base of an epicormic branch and Figure 6 showing conidia (spores) exuded from a dead twig infected with Discula destructiva. Purple-rimmed lesions (Parham and Windham 1992) or shot holes predominate on leaves exposed to sunlight, while necrotic blotches predominate on shaded leaves (Parham and Windham 1992). Leaf spots vary according to light exposure. 2 and 3), (2) shot holes, (3) necrotic blotches at the leaf tip or along the blade periphery, or (4) blight of the entire blade (Hibben and Daughtrey 1988) (Fig. Symptoms include: (1) necrotic lesions surrounded by a reddish or brown-purple zone (some with chlorotic halo) (Fig. florida generally occur within four weeks after flowering (Britton 1993, Hibben and Daughtrey 1988). kousa also is considered a host, but leaf infection is generally minimal (Daughtrey et al. Their loss could hasten soil acidification, reduce nutrient availability, and influence numerous ecological relationships (Daughtrey and Hibben 1994).ĭogwood anthracnose affects leaves, bracts, current-year shoots, localized areas of bark and cambium of the trunk or branches, fruits, and seeds of C. Dogwood leaves also have a high calcium content and decompose rapidly. Dogwood fruits, rich in fat and protein, are a preferred food for turkeys, bobwhite quail, squirrels, rabbits, and deer, as well as numerous non-game species of birds. Beyond this aesthetic loss, the absence of native dogwoods and their fruits is probably detrimental to wildlife. Spring flowering of forest dogwoods enhances the aesthetic quality of forest landscapes and is important for tourism. The decline of dogwood populations resulting from dogwood anthracnose has several serious impacts in the Southern Appalachians. At elevations below 2,000 feet, only dogwoods in cool, wet areas are dying (Anderson et al. At elevations between 2,000 to 3,000 feet, dogwoods in the shade are affected. In general, damage is most severe at elevations above 3,000 feet, where forest and ornamental dogwoods may be eliminated. Disease severity in the South seems to be more intense at higher elevations. In the GSMNP, it is estimated that more than 90 percent of the dogwoods have died in heavily shaded cove and alluvial forests. As of 1999, anthracnose had killed 49.7 percent of the native dogwood trees in 24 western counties of North Carolina (USFS 2001). During that period, the number of plots with severe epidemics (more than 25 percent of foliage blighted) increased by 638 percent.
Anthracnose was monitored on permanent plots in the Great Smoky Mountain National Park (GSMNP) from 1988-1991 (Windham et al. 1994, SAMAB 1996).ĭisease severity within infected areas also has increased rapidly.
Dogwood anthracnose has been reported on over 12 million acres in 180 counties (Anderson et al. By 1995, the disease had been confirmed in northern Georgia (1987), western North Carolina (1988), and as far south as northern Alabama. In the eastern United States, the disease has spread rapidly down the Appalachians, primarily on Cornus florida, the eastern flowering dogwood. Researchers also speculate that climatic changes and droughts may have predisposed trees to infection, thus causing coincidental outbreaks in the Northeast and the Pacific Northwest (Anderson et al. 1996).Īlthough the origin of dogwood anthracnose is unknown, the results of DNA analysis combined with its rapid spread have led many to conclude it was introduced (Daughtrey et al. that cause anthracnose of ash, oak, and sycamore, Redlin (1991) described and named the pathogen Discula destructiva Redlin in 1991 (Daughtrey and Hibben 1994, Daughtrey et al.
Finding the disease distinct from other Discula spp. Florida is now known as a major host that is impacted by this disease. nuttallii was identified as a species of Discula, and flowering dogwood ( Cornus florida) and Japanese dogwood ( Cornus kousa) were noted as minor hosts (Salogga and Ammirati 1983), but C. In 1983, the fungus associated with the anthracnose on C. Two years later, Pirone (1980) noticed a widespread and rapid deterioration of flowering dogwoods in New York and Connecticut (Fig. It was first observed in 1976 affecting a population of Cornus nuttallii in Washington state (Byther and Davidson 1979). Anderson, courtesy of .ĭogwood anthracnose is a relatively new disease to North America. Stem dieback from dogwood anthracnose ( Discula destructiva).