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Rhizoctonia Crown Rot and Cavity Spot of Muck-Grown Carrots. J. P. Mildenhall, Graduate Research Assistant, Department of Plant Pathology, University of Wisconsin, Madison 53706; P. H. Williams, Associate Professor, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 60:887-890. Accepted for publication 30 December 1969. DOI: 10.1094/Phyto-60-887.

A serious crown and root rot of muck-grown carrots in Wisconsin first appeared in the field when plants were about 5 weeks old. Isolations from crown and root lesions yielded isolates of Fusarium and Rhizoctonia. Greenhouse-grown carrots inoculated with the Rhizoctonia isolates developed typical crown rot and cavity spot lesions, whereas the Fusarium isolates were not pathogenic. Histological sections of lesions from field-grown carrots revealed abundant mycelium of Rhizoctonia adjacent to and within the tissue.