Velvetleaf, a New Host for Sclerotinia sclerotiorum. H. R. Dillard, Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456. A. C. Cobb, and B. T. Bozard. Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva 14456; and 11686 Ridge Rd., Medina, NY 14103. Plant Dis. 75:863. Accepted for publication 3 April 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0863B.
In 1990, velvetleaf (Abutilon theophrasti Medik.) was abundant
in some fields of cabbage (Brassica oleracea L. var. capitata L.) in
New York. Removal of this weed had been delayed because offrequent
rains in August and September. Several velvetleaf plants were observed
with white cottony fungal growth on the flowers and bleached areas
on the main stem and petioles. Sclerotia were present on the surface
of the affected stems and in the stem pith. Sclerotinia sclerotiorum
(Lib.) de Bary was isolated from symptomatic velvetleaf tissue.
Cabbage plants in direct contact with diseased velvetleaf also showed
symptoms of Sclerotinia rot. Sclerotinia rot of cabbage was previously
reported in association with infestations of ragweed in cabbage fields
(1). Velvetleaf plants were grown in the greenhouse for 11 wk until
blossoms were produced. A spore suspension (25,000 ascospores per
milliliter) of S. sclerotiorum was atomized onto the blossoms, and
the plants were incubated in a moist chamber for 10 days. The
symptoms that developed were similar to those observed on naturally
infected plants, and the pathogen was reisolated from the blossoms.
This appears to be the first report of S. sclerotiorum on velvetleaf.