First Report of Armillaria gallica Causing Armillaria Root Rot in Daylily in South Carolina

• Published in: Plant disease Vol. 89; no. 6; p. 683
• Main Authors: Schnabel, G, Bussey, K E, Bryson, P K
• Format: Journal Article
• Language: English
• Published: United States 01.06.2005
• Subjects: Armillaria gallica; Hemerocallis; USA, South Carolina
• DOI: 10.1094/PD-89-0683A
• ISSN: 0191-2917

Daylily (Hemerocallis sp.) plants declined in a homeowner's backyard in Walhalla, SC in June 2004. The backyard in northwestern South Carolina contained multiple, hardwood tree stumps, was surrounded by mature hardwood trees, and contained a dogwood tree showing symptoms of Armillaria root rot. Daylily plants were stunted and necrosis of leaves began at the leaf tips. A cross section through the crown of the wilting plants revealed necrotic areas with the presence of white mycelial fans. Rhizomorphs were found in the direct vicinity of the daylily root system, on the roots of the dogwood, and throughout surrounding soil. Diseased daylily crowns, rhizomorphs, and dogwood bark containing mycelial fans were collected. Small sections of white mycelial fans from daylily crowns and the dogwood sample were transferred to benomyl dichloran streptomycin (BDS) selective medium. Rhizomorph pieces were surface sterilized in a 0.6% sodium hypochlorite solution for 10 min and rinsed with sterile water before being transferred to BDS selective medium. Fungal cultures from all three sources looked similar on BDS medium and developed mainly crustose mycelium with some parts being aerial. After 1 week of incubation at room temperature in the dark, all cultures developed nonmelanized, mycelial fans that initiated from the center of the colony. The nucleotide sequences of internal transcribed spacer regions 1 and 2 and the intergenic spacer region 1 were identical for all isolates, and a BLAST search in GenBank of these sequences confirmed the identity of the pathogen as A. gallica (Marxmueller & Romagnesi) for both loci. To our knowledge, this is the first report of A. gallica causing disease on Hemerocallis spp. Our findings indicate that daylilies might be at risk for infection and should not be cultivated in soils containing rhizomorphs from pathogenic Armillaria species.