Disease Note

Powdery Mildew Caused by Erysiphe heraclei on Carrot in North Carolina. S. F. Jenkins, Departments of Plant Pathology and Horticultural Science, North Carolina State University, Raleigh 27695. J. Andreas, D. C. Sanders, and R. S. Gurkin, Departments of Plant Pathology and Horticultural Science, North Carolina State University, Raleigh 27695. Plant Dis. 70:892. Accepted for publication 16 April 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-892a.

Powdery mildew was observed on leaves and petioles of 12-wk-old carrot (Daucus carota L. var. sativa DC. 'Danvers 126') in September 1982 at Clinton, North Carolina. The fungus spread from initial foci throughout the entire 0.5-ha planting. The disease was more prevalent on older leaves, which became chlorotic and senescent. Growth and development of the fungus diminished with cooler temperatures in late October. Mycelium was well developed with numerous branches. Cylindric conidia, about 35–45 × 15–20 μm, were produced singly, rarely in short chains. Perithecia were not observed. Conidia germinated with unforked germ tubes, and fibrosin bodies were not detected. The anamorph fits the description of Erysiphe heraclei DC., the cause of powdery mildew of carrot and other umbelliferous hosts. The source of primary inoculum is not known. We have found no other reports of powdery mildew on carrot in the United States. Two applications of benomyl (Benlate 50W) at 280 g a.i./ ha controlled the disease.