Downy mildew of Rudbeckia fulgida cv. Goldsturm by Plasmopara halstedii in Virginia.
A severe foliage disease was observed on black-eyed Susan (R. fulgida) cv. Goldsturm in a commercial nursery in Virginia Beach, Virginia, USA, during early June 2005 and 2006. Typical symptoms were dark, blotchy necrotic areas on the upper leaf surface. Fuzzy, grayish white zoosporangiophores and zoosporangia were commonly produced on the underside of affected leaves. These symptoms were also observed on both sides of new leaves in severely affected plants. The causal agent was identified as P. halstedii based on the morphology and host specificity of the isolate. This is thought to be the first report of P. halstedii on R. fulgida from Virginia.