|
Disease Note Powdery Mildew of Carrot in New York. H. R. Dillard, Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456. A. C. Cobb, and N. G. Call. Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva 14456, and NGC Consulting, 7885 Lewiston Road, Batavia, NY 14020. Plant Dis. 76:972. Accepted for publication 4 May 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0972C. Powdery mildew was observed on leaves and petioles of processing
carrots (Daucus carota L. subsp. sativus (Hoffm.) Arcang. 'Oranza')
grown in Lyndonville, New York, in September 1991. The disease
was present in a single large area encompassing approximately one third
of a 16-ha field. Powdery mildew was most severe on the older
leaves, which were covered with white mycelia and conidia of the
fungus and senesced prematurely. Conidia were produced singly a~d
were 32-44 × 11-14 µm. Cleistothecia were not found, and fibroslll
bodies were not observed in the conidia. The fungus was identified
as Erysiphe heraclei DC. Infected leaves were gently shaken to dislodge
the conidia over healthy Oranza plants grown in the greenhouse, and
mildew colonies developed within 7 days. Weather conditions were conducive for development of powdery mildew during the 1991 growing
season, with mean maximum temperatures of 26, 28, and 27 C and
rainfall of 3.6, 3.4, and 5 cm during June, July, and August, respectively.
Control of the disease with fungicides was not attempted because
ofthe proximity of harvest. Yield in the affected field was not noticeably
reduced. In the United States, powdery mildew of carrot was previously
reported in California (1) and North Carolina (2). This appears to
be the first report of powdery mildew of carrot in New York State. |